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Found 39 results

  1. Hi all, I am needing some help with my 2003 yz250, i have posted a thread up a couple weeks ago about my bike bogging and having no power. I've listened to everyone's opinions on what is going on and have tried to fix it. Now, i'm needing some help with the cylinder and head, jets, and the power valve. 1. I am going to replace the reeds with power reeds, Will i have to rejet or anything? or can i just throw them in and ride? I'm doing a fresh top end so want the bike to be running good when i first start it. 2. I bought new jets cause the old ones were blocked. The new ones are the same size as the old ones, i can just throw them in and the bike will run the same as if the old ones were still in? or will i need to mess around with something? 3. Is the cylinder head in good shape or bad? Is the cylinder in bad shape? If so, what is the cheapest way for now and for future rebuilds to fix it? What type of cylinder is it? Sleeved?, nikasil? 4. The power valve looks like it has alot of oil/carbon in there, how do i clean it and what do i clean it with? As seen in video, when i pull the power valve to me it stays like that, i thought it is supposed to go back in?
  2. Freshening up the top end in your dirt bike or ATV is a critical part of preventative maintenance. However, it’s not as simple as purchasing a new piston kit and dropping it in. Properly preparing your cylinder is equally as important as installing a quality piston. Cylinder prep recommendations are always included with the piston when ordering from Wiseco. Depending on your application, it will either say “deglaze / hone” or “bore & hone” or “bore / replate.” We’ll take a look at exactly what these different terms mean and how to perform these steps. Deglaze your Cylinder A common question is “Do I need to deglaze my cylinder?” The answer is: yes, unless it’s time for a replate or resleeve. If you’re engine has any time on it, the glazing process has begun. The term ‘glazed’ in this context refers to the motion of the piston ring(s) flattening out and polishing the surface of the cylinder wall during normal operation. The more time on the engine, the more glazed the cylinder is going to be. However, depending on how much time is on your engine and what type of cylinder you have, you may need to replate or resleeve, which we’ll discuss next. Notice the shiny surface of the cylinder wall. This cylinder has become glazed over time. Plated vs. Sleeved Cylinders If your Powersports engine was made in the last 2 decades or so, chances are it is plated with a Nikasil (Nickel Silicone Carbide), chrome, or electrofusion plating. Nikasil has been the latest and most commonly used cylinder coating due to its wear resistance qualities, but they do still wear out. We recommend checking your manual for normal top end rebuild times, but generally if your engine has long hours, the overall condition of your cylinder will need to be closely reviewed. This will include not only the bore size and plating condition, but also the cylinder roundness and taper in reference to OEM service specifications. There are a number of good companies that offer replating services, just do your research and choose a trusted company. Your cylinder should come back with fresh plating, honed, and ready to go after a quick cleaning. This cylinder has been replated and prepped for the rebuild. The cylinder wall surface is no longer reflective and glazed-looking. Other forms of cylinders that aren’t plated commonly have iron or steel/alloy sleeves. If your cylinder does have a sleeve, you should be able to see the seam between the sleeve and the actual cylinder. If you’re still not sure, check to see if a magnet sticks to the cylinder wall. If it sticks, it’s a sleeve, and if it doesn’t, it’s plated. Much like replating a cylinder after normal top end rebuild time, your sleeved cylinder should have a new sleeve installed. The same cylinder shops that do replating should do resleeving as well, and it will come back honed and ready to go back together. In short, if your engine has enough time on it to need a full top end rebuild, we recommend replating or resleeving your cylinder. Technically you can have your previously plated cylinder sleeved, but we recommend sticking with how it came from the OEM. If it is just freshening up with low hours on the engine, you should be able to just deglaze / hone. What is Honing and Why do I Need It? When your engine was made brand new in the factory, the cylinder was honed. Honing is a process of conditioning the surface of the cylinder wall to help with lubrication of the piston ring(s) during operation. Honing creates fine cross hatch imperfections on the surface of the cylinder bore. You can think of these imperfections as peaks and valleys in the surface of the metal. These are essential because it helps the cylinder wall retain oil to assist with piston ring lubrication. Theoretically, the idea is for there to be a very thin layer of oil between the edge of the piston rings and cylinder wall. If there was no oil to lubricate the constant contact with the cylinder wall, there would be too much friction and both the rings and cylinder would wear out quickly. The term ‘deglazing’ simply refers to re-honing your cylinder to put those peaks and valleys back in your cylinder wall. This crosshatch pattern on the wall of the cylinder is the goal of the honing. How to Hone your Cylinder The most common tools you’ll find for honing small engine applications are rigid or brush hones and ball hones. Hones can be ordered by size according to your cylinder bore, just cross reference your bore size with the information from the company you order your hone from. The hone company should also have recommendations on grit and material type based on what type of rings you have. After disassembling your top end, inspect your cylinder wall and ports for damage. If you had a piston seizure or something break, chances are the cylinder was damaged. Depending on how extensive the damage is, sometimes cylinder shops can repair them. If you see any questionable damage or deep scuffs, we recommend sending your cylinder to a trusted shop for their best recommendation. If your cylinder is in normal condition with no damage, and you’re just changing rings between top ends, honing should be the only thing required. If the glazing is minimal and you can still see a fair amount of cross hatch marks, you should be able to get away with using a rigid or brush hone to just restore those cross hatch marks. You should only have to hone for about 10 – 15 seconds at a time until you can see consistent cross hatch marks. A soft hone brush like this is one of the tools that may be used to prepare the interior surface of the cylinder. The ball hone will be a little bit more abrasive, which is why we don’t recommend using a ball hone on plated cylinders unless they are specified to be safe. If you do need to use a ball hone for heavier glazing on your sleeved cylinder, attach it to your drill and lubricate it with a light coat of motor oil. Make sure the cylinder is secured and stationary, and the ball hone is spinning before entering the cylinder. Hone the cylinder back and forth for about 10 – 15 seconds, then switch to the opposite spinning direction and repeat. Check the cylinder for the desired cross hatch marks, and repeat if necessary. After honing is complete, be sure to clean the cylinder thoroughly until there is no residual material. When reassembling your top end, always be sure to double check your piston to wall clearance. Do I Need to Bore my Cylinder? If the instructions for your new piston say “bore & hone” or “bore / replate,” it’s because you ordered a piston that is larger than the stock bore size. Instructions to bore and hone your cylinder means your cylinder did not come plated from the OEM, and only requires to be machined out to the correct size for your piston. However, if it is a sleeved cylinder, consider having it resleeved depending on the time on the engine. Instructions to bore and replate your cylinder means your cylinder came plated from the OEM, so the only work required is to have the cylinder machined to the correct size for your piston, and then replated / honed. We recommend having your local trusted cylinder shop do your boring and replating work. In any case, we recommend having the cylinder bored by a professional machinist with the proper equipment. Cylinder shops that replate and resleeve usually have the capability to bore as well. Don’t Forget to Chamfer and Clean Up After any boring or honing work on a cylinder, it’s important to chamfer all ports and the bottom of the cylinder. Chamfering is smoothing out any sharp edge to leave a symmetrical sloping edge. Creating sloped edges on the bottom of the cylinder allows for easier piston and ring installation. You also want to make sure that the edges of the ports in the cylinder have a nice slope as well so the piston rings don’t get caught on any edges during engine operation. If your cylinder has an exhaust bridge, be sure it is relieved .002” - .004” to allow for expansion. Exhaust bridge relief is important in certain 2-stroke applications. Read more about exhaust bridge relief here. Lastly, be sure to properly clean any parts that have been worked on. Cylinders that have been bored and/or honed will have residual honing grit. This must be removed by washing with warm soapy water until an oil dampened cloth does not show any grit after wiping the surface of the cylinder wall. Once clean, apply a thin coat of oil on the cylinder wall before proceeding with your rebuild. Always be sure to cover all your bases when freshening up the top end in your machine. Giving the required attention to all areas will help you be sure you’re getting the smoothest performance and most reliability out of your engine.
  3. Hello! This weekend I opened up my 2004 yz125 and was pretty surprised by the condition of the parts. I ran it for a whole season and before that was PO's time on top which supposedly isn't more than 2-3 hours but never can be sure about that. I was thinking of doing a top end job on it but after seeing what it looks like I am tempted to run it another season. This is my first time opening up a bike hence why I am asking for advice. I will attach a bunch of photos of the cylinder, head, and piston. I was pleased by the very small amount of carbon build up on the piston crown and the extremely small amount of up down play in the rod. In fact I can't feel any play in the rod but only a tiny amount in the piston itself. None of the vertical lines in the jug catches my finger nails. I have quite a few questions that I will label with numbers to make answering easier. 1. Do you think this can run for another season? 2. Should I atleast change the ring? 3. What is the ring gap size supposed to be? (manual doesn't talk about it, unless I missed it) 4. The manual talks about aligning the ring gap with a small pin in the ring grove. Is this relevant since the ring will just rotate away anyway? 5. One of the circlips open end is near the piston pin slot but I can't rotate it away from it, is this okay? (both clips seem stuck) 6. Is the nikasil still good on the cylinder? (especially above the exhaust port it seems worn off) 7. kinda off topic, how do I unplug this connector? (image below) 8. Just as an extra, what should I look for in general when opening up a two stroke like this? Thanks alot in advance! I can get more pictures if any of you want to.
  4. Hey guys, I have a 1969 (approximately) Honda Z50. It was given to me after my uncle died. He would ride it around the dirt lake road between our families houses with a beer in one hand and a cigarette hanging out of the side of his mouth laughing the entire way. If you've ever seen or owned a Z50, they are a little ridiculous. All I wanted when I was younger was to ride his mini bike but I never got the opportunity. After he died, it sat in his garage for a number of years until i eventually came to own it. Unfortunately after sitting for so long, it is not starting at the moment. In addition he was not much of a mechanic so it needs some serious TLC. I thought it would be a great honor to restore it in his name and put it back on those lake roads. I need help guys. I can figure my way out around a bike but I am a little curious where to start with this old hunk. I would be happy to get it running again but I am also looking at possibly engine swapping this little guy (80cc or 125cc) if possible. And I know what you're thinking, "waste of time.. or this idiot has too much time on your hands"......agreed but I think you can agree that would be pretty badass. And for the short amount of time this thing gets used it would be a fun little project for nights at the lake. If you have any advice on where exactly to start or if the engine swap is possible please let me know. Not looking to hear from any of you automatic 'nay-sayers,' have a little imagination and appeal to your younger 12 year old self. Thanks, Chip
  5. Hello, I disassembled my engine to replace piston, bearings and seals and relied on my manuals too much. I didn't take a photo of the 3 shift fork positions and believe I have them installed properly but cannot find anything to guide me. Anyone familiar enough that can glance at the photos and let me know if they look correct? Photo angle is from the bottom of the engine, one of the forks has an L on it so it's obviously the left side when facing the engine bottom angle. I'm working on the other half of the engine in the meantime, hoping to get a tip to help me feel better so I can reassemble and take her for a spin!
  6. The clutch system is the most important connection between your hand and the rear wheel, as far as controlling the machine. When working properly, most riders don’t give their clutch a second thought. However, the importance of the clutch quickly snaps into focus when there’s a problem with the system. A clutch is an engineering marvel. Imagine you are on the starting line waiting for the gate to drop. You start your bike and pull in the clutch. What follows is a chain reaction of events. A series of moving parts transfer that load down to the clutch, where the pressure plate is pushed away from the clutch pack, basket and inner hub. At that point, there is a disconnection between the transmission and crankshaft. Clutch functionality involves a series of moving parts that are crucial to engine operation. Periodic maintenance, inspection, and replacement will keep your machine running as it should. Shown here is an exploded view from Yamaha of a YZ250 clutch. With the clutch disengaged, you click the shifter into gear. The gate drops, and you quickly release the clutch lever. The clutch springs force the pressure plate to squeeze the friction and drive plates together, causing the clutch basket and inner hub to synchronize. At that point, the energy generated inside the combustion chamber is carried through the transmission and to the countershaft sprocket, which then transfers the load to the rear wheel. Without an operating clutch, you would be sitting on the starting line as the pack raced away. Suffice it to say that your clutch is a vital piece of the overall puzzle. And, like most parts on your bike, it won’t last forever. Fortunately, there are three general indicators that your clutch is not working properly. You don’t need to be deft or dexterous to determine whether your drive system is giving up the ghost. The only necessities are a handful of tools, basic mechanical knowledge, and a good sense of smell. In this article, we delve into the symptoms, causes and solutions for the most common clutch problems so you can get back to riding. Sign #1: Slipping Away Symptoms: A slipping clutch is quickly recognizable when you’re twisting the throttle with reckless abandon while the machine is in gear, yet the rear wheel isn’t rotating in unison with the engine’s rpm. If you’re wound out in third gear and only accelerating at a snail’s pace, then something is wrong. You may also be able to notice a vague feel at the clutch lever. Either of these symptoms suggest that the internal clutch components need to be inspected for wear. Causes: When a clutch is performing optimally, the drive plates and friction plates are pushed together during clutch engagement (i.e. when the clutch lever is let out). The connection causes the rotation of the clutch basket and the inner hub to synchronize and work as one unit. However, as the plates begin to wear out, the clutch plates will slip against each other instead of grabbing. This prevents the transfer of energy from the engine to the transmission. Unfortunately, clutch slipping is inevitable, even if you aren’t a clutch abuser. Clutch plates wear out over time as a result of rubbing when the clutch is engaged. When experiencing clutch slipping, the likely culprit is worn clutch plates. It's time to disassemble and inspect your steel and fiber plates for wear. It is also possible that the clutch springs have lost their tension. When this happens, the springs aren’t strong enough to effectively pull the pressure plate against the clutch pack. Just as with clutch plates, clutch springs do not last forever. Worn clutch springs can also contribute to a slipping clutch. Read on for an explanation on inspecting your clutch springs. Solutions: When you experience clutch slippage, you’ll need to inspect the drive and steel clutch plates, as well as the clutch springs. To quote Dave Sulecki, Wiseco Powersports Engineer, “It’s very easy to access the clutch on all the new bikes. You can literally lay the bike over on its side, pop off the clutch cover, and start inspecting the components.” Using a vernier caliper or micrometer, measure the thickness of the steel (or aluminum) drive plates, and the fiber plates. Consult your owner’s manual to find the recommended specs. Be sure to also check the free length of the clutch springs. It’s a good idea to replace the drive and fiber plates, as well as the clutch springs. The most accurate way to know if your steels and fibers are worn is to measure them and compare the thickness to the recommended spec range in your owner's manual. Similarly, clutch spring free length can be measured to determine if they are outside of spec and need to be replaced. Replacement clutch components—both in individual components and clutch pack kits—are readily available through aftermarket companies like Wiseco. Replacing your fiber and drive plates at the same time is common practice, and when springs are required as well, all these components are available in kits with fibers, plates, and springs in one box. Each kit is built to OEM specifications and far less expensive, and Wiseco clutch springs feature a stiffer rating for a more positive clutch engagement. Replacement clutch components from Wiseco are available in individual packs of steels, fibers, and springs, as well as in clutch pack kits that include all three. Find Wiseco clutch components for your bike or ATV here. Sign #2: Creeping & Bad Smell Symptoms: The machine is emitting a foul burning smell that could strip paint off a wall. The stench might be so pungent that it’s evident after pulling into the pits. Generally, though, the smell is noticeable after removing the clutch cover. You may also notice your bike creeping forward with the clutch pulled in and the transmission in gear, no matter how much you adjust the clutch cable. Causes: Do the sniff test. Pull the clutch cover off. If you smell burnt clutch material, chances are your clutch will need new components. The burnt smell is the result of the clutch heating up. “The parts that burn first are generally the friction plates. It’s a real obvious odor. You’ll know it when you smell it. Visually, you’ll see the heat marks in the drive plates. The friction plates can also become black in color. The best thing to do is check the plates dimensionally against the specifications in your owner’s manual. Make sure you’re within tolerance on width and flatness,” states Sulecki. Burnt friction plates will typically become black in color and burnt drive plates commonly show dark colored wear marks. Solutions: For starters, you’re going to need to replace the oil. Be sure to pay close attention to the recommended service intervals in your owner’s manual. Doing so can extend the life of your clutch. Sulecki adds, “Fresh oil will help keep things lubricated and running cool. Oil does break down from heat and friction over time. In a lot of engines, the clutch shares oil with the transmission and valve train. Oil gets a lot of opportunity to break down quickly. Keep the oil fresh.” However, the damage of a cooked clutch cannot be undone. Clutch plates can warp over time from the heat. Warped plates cause the clutch to disengage unevenly and create all sorts of headaches. You will need to invest in new friction and drive plates, at least. However, heat could also damage the clutch springs, effecting spring tension. Be sure to inspect all your clutch components. If you find your clutch components have been subjected to excessive heat, it's always a good idea to at least replace the drive plates, fibers, and springs (when applicable). Sign #3: Feeling A Drag Symptoms: The clutch lever feels lumpy during clutch engagement/disengagement. Sometimes the lever can feel jerky. These are telltale signs that the clutch basket and/or inner hub is damaged and needs inspection. Causes: If your machine has the OEM/stock clutch basket, it was likely made using a diecast aluminum material. While fairly lightweight, durability is not stellar. “When you cast aluminum, you take molten aluminum and pour it into a mold. Once it has solidified, it gets processed from there into a finished part. When the material is molded it is generally not very dense. You get a lot of voids, porosity, inclusions, and imperfections in the material. The constituents inside the material aren’t bonded tightly against each other,” states Sulecki. The most common wear on cast clutch baskets is notching on the edge of the tangs where the clutch plates engage. The inner hub can be inspected for similar wear. If you see notching like this, it's time for a replacement. Solutions: There are a variety of aftermarket clutch basket options that use different manufacturing processes. Billet is a common alternative to casting, but even that has downfalls. Sulecki explains, “With billet, you’ll start with a cast piece of aluminum. It will generally get compressed a little bit in a forge press or some sort of pressure casting. That’s to condense the material a little tighter. Then the part is machined from the solid piece of metal. It has slightly better properties than a cast part, but not as much as a forged part.” Forging is a very intricate and involved process. It begins with a cast and drawn bar of aluminum material, which is then smashed until all of the molecules are bonded to each other. This makes the material much denser and creates what engineers refer to as feature aligned grain flow. Basically all of the grains in the material are forced to flow up through the features–particularly the tangs on the clutch basket and stanchions on the inner hub–for greater strength. All of the material properties improve–from tensile to fatigue to ultimate strength. Ductility is also improved, meaning the material can bend before it breaks. Cast and billet constructed clutch baskets are susceptible to wear. This is why Wiseco forges their clutch baskets in house before machining them, achieving greater tensile strength and wear resistance. Sulecki adds, “The denser material is very resistant to impact and fatigue, which are two critical components of a clutch basket. Impact is caused by the clutch plates as they drive against the tangs on the clutch basket. Clutch plates will actually start to create indentations on a stock cast part, and dimples on a billet basket. In turn, the plates can’t slide smoothly across the width of the tab as you pull in the clutch lever to disengage the clutch. A forged clutch basket’s resistance to impact means that it will not develop notches in the tangs.” Suffice it to say that forging is the superior material for clutch basket durability and lasting performance. Check out all the technical details on Wiseco clutch baskets here. The forged material creates much greater resistance to impact from the clutch plates during operation, providing a seemingly lifetime solution to tang notching. To cap it off, Wiseco hard coat anodizes and coats their forged clutch baskets with Teflon. Hard coat anodizing aids in wear and abrasion resistance, as well as improves lubricity and corrosion resistance. Teflon coating is the last process. It helps fulfill the wear resistance and lubricity that Wiseco requires for their clutch baskets. Hard coat anodizing and teflon coating finish off Wiseco clutch baskets for ultimate wear resistance and smooth operation. Find a Wiseco clutch basket for your machine here. Lifetime Guarantee It’s interesting to note that Wiseco has been manufacturing forged clutch baskets, pressure plates and inner hubs for years, but this all-too-important detail has flown under the radar. “Our forged clutch basket is the best product we make that nobody knows about,” says Sulecki. The performance-driven powersports magnate is so resolute in the durability of their forged clutch baskets that they offer a lifetime guarantee against notching and breakage. What does that mean? You’ll buy it once and never have to worry about it again. Related Reading: How to Replace the Clutch Basket in your Motorcycle
  7. I have a 2002 drz400s that just hit 11,500 miles. I've owned it about 1000 of those miles and they were done some highway, some urban street and some trail. I had an issue a while back with the float needle seat o-ring letting fuel into the oil, changed the o-ring and that seemed to be the end of it. At first the bike wasn't running great but after fixing that carb issue, a 3x3 mod and a JD jet kit I'm in love with this machine...which is why I'm very concerned about her drinking oil!!! Ive noticed over about the last 300 miles or so it has gone from full on the dip stick to about half. This morning I took her around the block to get her all warmed up and check the oil and it was about 3/4 of the way up the stick. This afternoon I did about 40 miles highway and 20 miles trail and came back and checked and it was half. I decided to dump a little oil in there until it read full on the stick. I"m confused because the bike is running pretty well and if it was drinking that much oil and had bad rings I would think this would be noticed. There are no leaks on the floor of my garage or any signs on the engine thats its leaking, also no sign of oil in the exhaust. So ...What could it be, is it immediately serious, and can I just keep adding oil and get another 1000 miles out of it before I have to rebuild her?
  8. Hey, internet. I am rebuilding a 2009 Yamaha yz250f. I bought it blown up from another guy. I took the motor out of the bike for ease of rebuilding. The head was destroyed so it got a brand new head, entire valvetrain, cams, piston, new spark plug, and I honed the cylinder. Once I got everything back together, I put it in the bike. I hooked up all the electronic plugs to the bike and timed the motor then. No start. I talked to a couple guys and they thought I might have been off 180 degrees on my timing, so i took the cams out, rotated the motor over once, then reinstalled the cams. Still no start. I tried the old spark plug, no start. I put the plug in the ignition coil out of the bike and it made a good spark, on both plugs. I also have a 2007 Yamaha wr250f with the same motor, tried the ignition coil off that, no start. I reshimmed the valves, I might have had a too big shim leaving the valve slightly open. No start still. I've retimed the motor about 5 times now, with no success. I also went through and cleaned the carb. As of now I don't have the air filter on it. I opened the throttle all the way and gave it some starting fluid to get at least one fire. Still nothing. I got a bit of gas and dumped it down the spark plug hole, nothing. I haven't had one single fire since rebuilding it. I'm out of ideas, any suggestions?
  9. Well it’s been almost a year since I’ve gotten this bike, and I can say I’ve truly enjoyed the process. Thank you for the help you guys have given me and I figured I’d. Come back to share the transformation. (Black being before & Blue Being after) since these pictures I have changed the seat and seat cover, cutting it down half inch and with a FLU design seat cover Edit: yes I know this isn’t the best rebuild at all, but it’s the best I could do for the budget. Also if anyone could list some pretty good cheap modifications or parts that’d be gladly appreciated
  10. I bought this bike around a month ago and am just getting around to posting it. This will hopefully be a full rebuild thread. Keep in mind that I am a broke 15 year old and will update as I have time. The bike is a 1999 KX125. Paid $500 for it. Supposedly only needed a top end and to have the brakes filled back up with fluid and bled. The previous owner gave me the old piston. He said that he drained the brake fluid because he took the wheels off to put on new tires. It will be my first big bike that I've fixed. The bike came with a full tank of gas and a center stand. It also came with a side stand. I checked all the big things, chain and sprockets were good, it kicked over, tires looked new, pipe looked undented. I realized it had a broken throttle tube, it was missing the silencer, needed misc bolts, shift lever, air filter. Nothing big (yet). It looked like a great bike to fix up and sell. After looking at it in more detail, I have come up with a theory about its background. I think it raced by a guy who knew what he was doing. Then, it was crashed hard, guy got scared and sold it to the guy that I bought it from. The guy that I bought it from only had it for a week and got married. His wife was making him sell it. Maybe he'll be on here and recognize his bike. It has ProTaper bars, Boyseen reeds on stock cage, rear Excell rim, Front D.I.D. rim, Pro Circuit expansion chamber, P3 pipe skid plate, Motion Pro stickers. Just little things that add up. Crashed parts: Broken throttle tube, cracked clutch lever perch, broken rear brake fluid reservoir tab, bent rear brake disk, front brake blew, took out the 2 subframe bolts that hold the seat and rear plastics on, one side seat tab ripped out of seat, no air filter, rear fender airbox cover broke, no shift lever, no air filter, new D.I.D. front rim. I think the crash took out quite a few things, and he bought new ones to sell.
  11. Top-end rebuilds are a necessary maintenance task associated with high performance off-road two-stroke motorcycle ownership. The common belief is that performing a top-end rebuild is a simple task that anyone can do, which is true, however, the devil is in the details. Sloppy, incomplete, or top-end builds done wrong can jeopardize performance, reduce reliability, and ruin the bottom end in the process. At Wiseco, we’ve been manufacturing top-end two-stroke engine components for decades and have been building engines for just as long. To ensure your Wiseco top-end parts run trouble free, we’ve put together some top-end rebuild tips that will ensure your next build is your best build. These tips will be discussed chronologically and will encompass all phases of the build from diagnosis and preparation, to disassembly, through post build. The tips we’re going to share shouldn’t be considered inclusive of everything that has to be done but are tips that focus on things that are either often overlooked or incredibly important. Let’s dive in! Before Teardown Pre-teardown activities can be an insightful way to help pinpoint any internal issues and prepare for upcoming work. Check out these three pre-teardown tasks that will streamline the whole process. Diagnosis - Before tearing the engine apart, are there any signs that a specific problem exists? If so, are there any diagnostic tests such as compression or crankcase leak down that are worth performing? Service Manual - Performing engine maintenance without an OEM factory service manual is not recommended. Make sure you have a manual for your machine prior to starting work. The manual is the only place you’ll find service limits, torque specs, and other key data. Clean Machine - Take the time to thoroughly clean the machine before opening up the engine, especially if you will be servicing the top-end without removing the engine from the machine. Need some tips on knowing when to replace your piston? We have a guide here. It doesn't have to be spotless, but cleaning off excessive dirt and mud can make it a lot easier to keep debris out of citical components during your rebuild. Disassembly Perform disassembly steps methodically and be cognizant of the fact that the bottom end of the engine will be exposed to the elements. Take every precaution to ensure dirt, debris, and hardware does not get into the bottom end. Bearings and other running surfaces have an incredibly low tolerance for dirt, no matter how little. Protect the bottom end - Once the cylinder has been removed, wrap a clean, lint-free rag around the top of the crankcase. Keep your bottom end components protected with a clean rag covering the exposed crankshaft opening. Piston removal - Easy piston circlip removal can be accomplished by using a pick and needle nose pliers. Insert the pick into the dimple in the piston and behind the circlip, then use it as a lever and pry the circlip part way out. Once part way out, grab the circlip with needle nose pliers. During this process, be careful not to scratch or mar the wrist pin bore, as this will make removing the wrist pin much more difficult. The ease of pin removal will be largely dependent on the engine design and condition of the bore. If the pin can be removed by hand, great, if not, light tapping while supporting the rod is permissible. Otherwise, a pin puller should be utilized, which can be bought or made. In its simplest form, this can consist of an appropriately sized bolt, nut, and socket. Once the wrist pin has been removed, the piston can be removed from the rod. Removal of your old piston should be carefully handled. Cautiously remove the circlip and the wrist pin to get the piston off the connecting rod. Carelessness during this step could damage your connecting rod or crank. Power Valve Disassembly - Prior to taking the power valve system apart, spend some time reviewing the procedure in your service manual. For additional insight into how the components interact, review the exploded views in the service manual and look at part microfiches which can be found online. When removing the power valve system, consider laying the components out on a clean sheet of paper in an orientation that correlates to how they are installed in the engine. This is a relatively simple thing to do that will help you remember how they are installed later. When it comes to cleaning the components, clean them one at a time or in small batches so that they don’t get mixed up. Take note of how your powervalve is assembled and operates before taking the components off for cleaning. Inspection Meticulously check all the top-end parts to ensure they are in good working condition. Rotate the crankshaft by hand and feel for smoothness in the crank and rod bearings. Review the items below for often overlooked inspection opportunities. While the top end is apart, inspect your connecting rod and crankshaft to ensure everything is in good operating order. Reed Valve - Don’t forget to check the condition of the reed valve petals, cage, and any stopper plates. Most service manuals will detail the acceptable clearance between the petal tips and cage as well as the stopper plate height. Ensure any rubber coatings on the reed cage are in good condition. Intake Manifold - Check the intake manifold for cracks. Cracks are more common on older engines, and if they propagate all the way through the manifold, can lead to air leaks. Exhaust Flange - Check the condition of the exhaust flange and ensure that it is not excessively worn. An excessively worn flange will make exhaust gas sealing difficult, hamper performance, and leak the infamous spooge. Power Valve Components - Take a moment to review the condition of all the power valve components. Significant wear can occur over time and lead to performance losses. Rod Small End - Check the small end rod bore for surface defects such as pitting, scratches, and marring. Any severe defects in the bore will necessitate rod replacement. New Parts Once you’ve disassembled the engine and have a full picture of any issues, make a list of everything you’ll need to replace. At the very least, you’ll likely be replacing the piston and top-end gaskets. Forged piston kits are available from Wiseco for a wide range of applications, and include the piston, ring(s), wrist pin, and circlips. Many applications can also be purchased with a complete top-end gasket kit from Wiseco. Wiseco pistons are available with features and pricing ranging from reliable replacement to race-focused. Replace your top end with quality components. Shown is Wiseco's Racer Elite two-stroke piston kit. Check out everything Wiseco offers for your machine here. Trying to decide between single-ring and two-ring? Check out our explanation here. Measurements The number of measurements that should be taken throughout the top-end rebuild will be discretionary. At Wiseco, we strive for excellence and err on the side of caution when it comes to engine building, so our builds consist of numerous measurements and inspections prior to reassembly. For us, this ensures a high level of confidence and safeguards against external oversights. We recommend the same to anyone building an engine. Below is a list of measurements that we routinely make when rebuilding a two-stroke top-end: Piston ring end gaps Checking ring end gap involves inserting the piston ring into the bore and using feeler gauges to determine how large of a gap there is. You should compare your measurement to the spec outlined in your owners manual or piston instructions. Rings commonly come pre-gapped, but some fine-tuning may be required after measuring. Ring end gaps should be filed evenly, small portions at a time to reach the desired spec. Piston ring to ring groove clearance This measurement is double-checked by Wiseco during manufacturing, but it never hurts to double-check. Ring to ring groove clearance should also be checked and compared to the recommended spec in your manual/piston instructions. Piston to cylinder clearance Measuring piston to cylinder wall clearance involves measuring the diameter of the piston and subtracting that from the bore diameter. Be sure to follow your piston instructions on measuring your piston at the proper gauge points. Wrist pin to piston clearance Please note, pin fit is done by Wiseco during manufacturing, but if you have the tools, it's always a good idea to double check. Making sure your piston has proper clearance involves measuring the wrist pin diameter and subtracting that from the pin bore diameter. This can accomplished using a bore gauge set and a micrometer. Rod small end diameter Power valve components Out of these measurements, confirming or adjusting the ring end gaps is by far the most important, followed closely by ensuring the cylinder bore is within spec with respect to diameter, straightness, and roundness. Understandably, some measurements may be difficult for the average home builder to execute, usually due to not having the right equipment, however, a competent shop should be able to assist. Prep Work Before putting everything back together, take the time to prepare individual components so they aren’t overlooked or forgotten. Cylinder Cleaning - Once the cylinder has been deglazed or has come back from replating, it should be cleaned one final time. There is almost always leftover honing grit that will need to be removed. To effectively clean the cylinder, use warm soapy water and a bristle brush followed by automatic transmission fluid and a brush or lint-free rag. To check the cleanliness of the cylinder, rub a cotton swab around the bore and look for contaminants. Clean the bore until no contaminants are visible on the cotton swab. Any honing grit that remains in the cylinder will facilitate premature wear of the piston rings. Cylinder prep is incredibly important for a top end rebuild. Make sure your cylinder's plating is in good condition and it is properly deglazed, honed, and cleaned. Read our complete guide to cylinder prep here. Does your cylinder need the exhaust bridge relieved? We explain that here. Power Valve Function - Cylinders that have been exchanged or replated should have the power valve system reinstalled ahead of final installation. Often times, excess plating can inhibit power valve movement. To correct this, the excess plating must be carefully removed. On cylinders utilizing blade style power valves, the blade position with respect to the cylinder bore should be checked to ensure the blade does not protrude into the bore. Make sure your power valve is reassembled and functioning properly before reinstalling the cylinder. Piston - It is usually easiest to prepare the new piston as much as possible by installing one of the circlips and the ring pack ahead of joining it to the connecting rod. Unless your service manual dictates which circlip must be installed first, choose the easiest installation orientation. Typically, your dominant hand and preferred work orientation will dictate which side you choose to install the circlip on. Reference your service manual to determine the correct orientation of the circlip. Usually, the open end of the circlip should be oriented to the 12 or 6 o’clock position. Temporarily install the wrist pin and use it as a backstop so that the circlip is forced to move into its groove. Installing the circlip should be done by hand to limit the chance of deformation. Orient the circlip to the desired position, then push the open ends of the circlip into position first. Be careful not to scratch or mar the wrist pin bore in the process! Once installed, use a pick or screwdriver to confirm the circlip is fully seated and does not rotate. Any circlips that can be rotated must be replaced because they have been compromised and deformed during installation. It's easiest to install your ring pack and one circlip before installing the piston on the small end of the rod. Rings - The compression ring(s) will be directional, and the top of the ring is typically denoted by markings near the end gaps. Apply a thin coat of oil to the ring, then carefully work the ring into position. Ensuring the ring end gaps are lined up with the locating pins is crucial to proper 2-stroke engine operation. Read more about locating pins here. Installation Carefully work through the installation process by paying attention to the small details. Double check instructions and don’t force anything that feels abnormal. Be especially careful when mating the cylinder to the piston assembly. Piston - On the top of the piston, an arrow will be imprinted, which typically denotes the exhaust side of the piston. Consult your service manual and/or instructions that came with your piston kit to confirm the proper orientation of the arrow and piston. Apply a light amount of assembly lube to the small end bearing and wrist pin bore on the piston, then install the bearing, align the piston with the small end of the rod, and slide the wrist pin into place. Once again, use the wrist pin as a backstop then install the remaining circlip into position. Use a pick or screwdriver to confirm it is fully seated and does not rotate. When installing the new piston on the connecting rod, make sure the piston is correctly oriented, usually with the appropriate marking facing the exhaust side. Also, apply lube to the new small end bearing and wrist pin bore. Cylinder to Piston - In most applications, a ring compressor is not required to compress the rings and install the piston into the cylinder. Lightly oil the cylinder bore with assembly lube or engine oil. Then, lube the piston skirt and ring faces. Prior to installing the piston and rings, confirm one final time that the piston ring ends are oriented correctly to their respective locating pins. Before sliding the cylinder onto the new piston, apply some lube to the piston skirts, ring faces, and clyinder wall. It's critical to make sure the ring end gaps remain correctly oriented with their locating pins throughout cylinder installation. Position the piston at or near TDC, then carefully lower the cylinder bore down onto the piston. Use your fingers to compress the ring(s) and ensure the cylinder bore is square to the piston. Feel how easily the cylinder slides over the piston and rings. The installation of the cylinder should be smooth and offer little resistance. If resistance is felt, stop immediately and assess the ring pack. Occasionally, one of the rings may come out of position in its groove and snag the cylinder bore. This typically happens as the ring transitions out of your fingers and into the cylinder bore. When installed correctly, the new piston should move smoothly up and down in the bore without any snags or notchiness. Always make sure to torque your cylinder and head bolts to the spec outlined in your owners manual. Tighten the head bolts in a star pattern to prevent warpage. Post Build Before firing up your fresh top-end, do these three things to ensure the engine performs optimally. Crankcase Leak Down Test - As one final precautionary measure, perform a crankcase leak down test. A crankcase leak down test will help confirm all the seals, gaskets, and joints are sealing as they should. Spark Plug - Don’t forget to install a new spark plug, and, if necessary, gap it appropriately. Air Filter - Be sure to install a clean air filter prior to start up. A crankcase leakdown test can help ensure your new rings are sealing properly before initial fire up. Ready to break in the engine? Check out our complete motorcycle engine break in guide here. Wrap Up Top-end rebuilds shouldn’t be taken for granted or oversimplified since they deal with the heart of the engine. With adequate preparation, the right tools, attention to detail, and the appropriate knowledge, top-end rebuilds can be performed by anyone and yield great results. At Wiseco, we’ve performed countless engine builds and hope the information we’ve shared makes your next engine build go smoothly and successfully. This YZ250 engine is ready to rip like new again with a fresh Wiseco top end!
  12. Profile and ovality are two main characteristics of piston design. Here we'll take a look at why pistons are designed to not be perfectly round. When you look at a piston, it is easy to think that they are a perfectly round, cylindrical shape. After all, they go into a round hole (the cylinder!) So why shouldn’t they also be round? The fact is, the external shape of a piston is very sophisticated. An internal combustion engine is a hostile environment where combustion gasses can reach dangerous temperatures, and there could be port windows and surface undulations from uneven cylinder cooling. Designing a piston that is optimized for combustion chamber conditions is an important challenge. Throughout the years, piston materials and design characteristics to compensate for expansion under heat have evolved. Forging pistons out of aluminum provides great strength and durability, but it must be used in the correct design to properly optimize the performance of the piston. (Left) These are an example of early piston design, using steel as the primary material. These would not be sufficient for the requirements of modern engines. Compare with the variety of modern forged aluminum pistons from Wiseco (right) featuring different coatings and designs. Read more about the forging process here. There are two major characteristics of piston shapes: profile and ovality. Wiseco's Product Manager and long time engineer Dave Sulecki commented on these piston characteristics: “Piston profile and ovality are one of the most important features of a piston, these really determine not only how the piston will wear over time, but also how well the piston can perform. When the engineer calculates the piston to cylinder clearance, this is only the beginning of a complex determination of the final piston geometry." Profile If you roll a piston across a flat surface, you'll notice it does not roll in a straight line. You are observing characteristic number one: profile. Because aluminum conducts so much heat, pistons are designed with a taper -- the top of the piston, near the crown, is a smaller diameter than the bottom of the piston, near the skirt. The skirt of the piston actually is designed with what is called a barrel shape, illustrated below. This is beacuase temperatures near the dome of the piston vary from the temperatures at the skirt of the piston, resulting in different levels of expansion. The tapered shape allows the piston to expand as heat is applied, so the piston does not bind in the cylinder bore. The higher the temperature, the more the piston will expand. The design challenge then becomes calculating the degree of taper. Too tight of clearance can induce scuffing or seizure from heat expansion, while too loose of clearance can introduce noise from piston rock. This illustration shows piston profile: the barrel shape and taper pistons have. Because of this, measuring diameter on the skirts yields a larger number than measruing near the dome. "The piston profile is critical to how the piston will support itself as it reciprocates in the cylinder bore. For example, the piston profile must help hold the piston vertical in the bore during combustion; imagine any excess leaning of the piston would allow piston rings to become “unseated” and not seal properly against the cylinder wall," elaborates Sulecki. Ovality As you roll the piston across the table, you will also observe the piston rising and falling in a “hump-hump-hump” motion, much like a wheel that has a flat spot. This characteristic is called ovality, also known as camming. In the simplest terms, ovality means that the piston is smallest in line with the wrist pin bore. As the engine begins its movement, the connecting rod is not moving only up and down, but due to the rotation aspect is simultaneously moving sideways. This action from the connecting rod and the motion of the crankshaft place load forces on the piston along the plane of the connecting rod inline with rotation (known as the “thrust axis”). To allow the piston to move freely with this sidelong force, the piston cannot be perfectly round, or it would bind in the round cylinder bore. By applying ovality to the piston, the piston is free to move up and down as needed. The challenge in design is applying the proper amount of ovality. Too little ovality can cause the piston to contact the cylinder wall nearest the end of the piston pin, while too much ovality can cause the piston to ride too heavily against the cylinder wall along this “thrust axis.” Too much load along the thrust axis can result in heavy scuffing or seizure, when the piston breaks the oil film barrier and contacts the cylinder wall directly. This illustration shows piston ovality. The solid-lined ellipse represents the diameter of the piston as if you're looking down onto the dome. Dave Sulecki commented on ovality, "Ovality is an unknown thing, when most people look at a piston they think it is round, and to the naked eye this must be the case. However, take a new two stroke piston and roll it across the table and what happens? You will see the uneven “hump, hump, hump” as the piston rolls in a large arc…you are seeing both the profile (the “cone shape” of the piston”, in combination with the ovality as the piston rolls unevenly. Ovality is necessary for the piston to move up and down in the cylinder bore, as the crankshaft and connecting rod try to force the piston upward, and combustion forces the piston downward, ovality allows the piston to move without binding in the round cylinder bore." Your bike's engine need a complete rebuild? Or maybe just a piston and valves? Check out our Garage Buddy line of rebuild kits. Another visual representation of piston profile and ovality. Ovality is a key detail to remember when measuring piston size. The piston must be measured at the bottom of the skirt, 90 degrees from the wrist pin hole to reach an accurate measurement. When measuring piston diameter, be sure you’re using the proper tools. Do not use calipers to measure your piston(s), as you won’t get an accurate measurement. The most accurate tool to use is a set of outside diameter micrometers. Your piston should be measured at the bottom of the skirt, 90 degrees from the pin hole. Please note: The measurements displayed here are for representational purposes only. Measure each of your own individual parts for accuracy. Some Wiseco pistons feature proprietary skirt coatings such as ArmorGlide or ArmorFit, which are designed to reduce wear, provide smoother and quieter operation, and are applied to last for the life of the piston. With certain skirt coated pistons, piston-to-wall clearance measuring specs will change, so be sure to read the instructions that come with your piston(s). Click here to find out more about Wiseco's different coatings.
  13. The piston is one of many wear items in your powersports machine. It may last longer than tires or a chain, but it should still be treated as normal maintenance when the time comes. Here, we go through key tips to help you know when it's time for a refresh. The piston in an internal combustion engine is arguably one of the most important components found in the engine. When it comes to high-performance engines used in powersports applications, it is also a component that is regularly replaced and serviced. Knowing when your piston should be replaced and how it wears is key to maintaining a reliable engine. To help you make that decision, we laid out replacement intervals, piston wear, why it’s important to replace the piston, and piston replacement options. Piston replacement intervals are typically outlined in your machine’s factory service manual. Using dirt bikes as an example, many manufacturers outline a piston and ring replacement schedule of every six races or 15-30 hours for a four-stroke, depending on the machine. If you’re new to the sport or have never looked at your factory service manual, these service intervals may seem shockingly short. The service intervals are based on the service schedules required to maintain a high-level racer’s machine. Unfortunately, for the average rider, the outlined service intervals commonly end up being conservative. The recommended piston service intervals outlined in your manual may be shocking, but the actual required service time depends on many variables that differ by each rider. In reality, piston replacement intervals should be established based on how the individual owner rides and maintains their machine. It’s true that forged pistons exhibit greater strength and wear resistance, but the variables of rider and maintenance still apply. Engine displacement, engine make, air filter maintenance, environmental conditions, riding style, and the type of riding the machine is used for will all influence how long the engine should be operated before servicing it. Monitoring the engine’s health through periodic checks such as compression and leak down tests is the best way most riders can appropriately time major service tasks, such as piston and ring replacement. Due to the number of variables that affect engine wear, it is simply not possible to specify a replacement schedule that fits everyone’s needs other than a very conservative schedule. Realistically, there are too many variables to establish an official recommended piston replacement time. Sticking to the short time recommended in the manual can be overkill for some, but keeps things on the safe side. (We are not endorsing dry assembly with this photo, it was just mocked up for photo purposes.) Piston wear will typically occur in four key areas for both two and four-stroke engines, which include the piston skirt, wrist pin bore, ring grooves, and piston crown. The next time you disassemble your top end, keep an eye out for these wear points. Piston Skirt Wear Nowadays, on four-stroke engines, the piston skirt is very short and limited to the major and minor thrust faces of the piston. For reference, the thrust faces correspond with the intake and exhaust valve sides of the cylinder head. Two-stroke pistons use the same nomenclature, but feature much longer, more pronounced skirts. Piston skirts experience load on the major and minor thrust sides, resulting in wear in those areas. Piston skirt wear occurs because of the thrust loading that results from the inherent geometry of the crank mechanism as the engine fires. Peak combustion pressure occurs slightly after top dead center, which causes the piston to thrust into the cylinder wall. Skirt wear can be observed both visually and by measuring the skirt’s diameter and referencing it against the diameter outlined in your service manual. Skirt wear will appear as a polished area on the major and minor thrusting faces of the piston. Notice the polished-looking wear marks on the forged piston on the left, and the vertical wear marks on two-stroke cast piston on the right. These reflect wear after a substantial amount of run time. The grooves on the two-stroke piston are a potential sign of dust/dirt in the cylinder. Your pistons may feature one of a few different types of skirt coating. Wiseco pistons utilize different types of skirt coatings depending on the piston, including ArmorGlide and ArmorFit coatings. These coatings are screen printed on and are applied to remain on the skirt for the life of the piston. You will likely see some wear on the skirt coating after putting time on your piston(s), but if it is worn all the way through the coating, there’s a good chance there’s an underlying issue that needs investigation. Too little clearance, foreign material in the cylinder, and improper cylinder preparation could be causes of excessive skirt wear. This piston is equipped with ArmorGlide skirt coating. However, the wear patterns are indicative of the possibility of foreign material, such as dirt, making its way into the cylinder. On two-stroke engines, skirt wear can occasionally be heard audibly while the engine is running, which is commonly known as “piston slap”. A rhythmic metallic sound often accompanies a loose or worn piston when the engine idles. What can be heard is the piston rocking back and forth in its bore as it reciprocates. Piston Crown Piston crown wear will occur as a result of aggressive or improper tuning, and on four-stroke engines, a damaged or mis-timed valvetrain. Engines operated with a lean mixture at full throttle will see abnormally high combustion temps, which can cause detonation. The results of detonation will be visible on the piston crown as a pitted or eroded surface. The pitting in the center is a pretty clear sign of detonation. In many cases, pitting and erosion will be much more evident the leaner the running conditions. Piston crown damage due to valvetrain contact will be visible as indentations or cracks near the valve pockets. Valvetrain contact can occur due to valve float caused by excessive RPM or mis-timed valves. Notice the half-circles in the valve reliefs. This is a clear sign of valve contact with the piston. Ring Groove Wear The piston rings move in and out of their grooves because of the ignition of the air/fuel mixture in the combustion chamber. Once the mixture is ignited, the cylinder pressure increases which energizes the compression ring and forces it against the cylinder wall, causing it to slide in its groove. On four-stroke engines, the compression ring will transition from seating on the bottom of the ring groove to the top ring groove at the end of the exhaust stroke due to forces of inertia acting on the ring. Ring movement during operation will eventually wear ring grooves beyond their designed size. Substantial run time can also leave carbon deposits in the ring grooves, affecting ring seal and performance. Ring and groove wear can occur due to the sliding and reciprocating motion of the rings and can be exasperated by carbon deposits that accumulate in the ring groove. Ring and groove wear can be qualified by thoroughly cleaning the ring and groove and then measuring each. Most service manuals outline specifications for ring width, groove width, and piston ring to ring groove clearance. Ring wear can be easily visually observed, but can be confirmed by taking axial height and radial width measurements and comparing them to the original spec. Wrist Pin Bore Wear Wrist pin bore wear occurs as a result of the loading of the wrist pin joint through inertia and combustion loading. The wrist pin bore will typically wear into an oblong shape. In some engines, wrist pin bore wear will be visible in the top and bottom of the bore. Usually, a portion of the bore will appear burnished or polished. Alternatively, the wrist pin bore can be measured from top to bottom and from side to side. Both measurements can be compared to one another to determine how much the bore has become out of round and to the diameters specified in the service manual. Wrist pin bores typically wear into a vertical, oval shape due to the pushing and pulling forces of engine operation. Visual inspection can show excessive wear, and a vertical and horizontal diameter measurement can tell you how out of round it is. If it's proving out of round, it's probably time for a replacement. The importance of replacing the piston at regular intervals in high-performance powersports engines cannot be overstated. If left unattended, the resulting cumulative wear of the piston will eventually result in a catastrophic and expensive engine failure. Typically, too much time on a piston can lead to gradual and finally complete failure of the skirt in both two and four-stroke engines. Between aftermarket suppliers and OEMs, replacement piston options are plentiful and can be overwhelming. The most common upgrade and consideration most riders are faced with is whether or not to move to a forged piston. Forged pistons can be a nice upgrade for many riders because they can offer additional strength and wear resistance over cast pistons. Forged pistons achieve greater strength than cast pistons by using different aluminum alloys and manufacturing processes. The forging process for pistons results in finished components that have a tighter molecular structure and grain flow optimized for strength. Comparatively, cast pistons are not cast under high pressures and have molecular structures that are not as tight or organized, which in severe cases, can lead to voids, inclusions, and air pockets. Forging pistons results in a better-aligned grain flow and higher tensile strength. Read more about how Wiseco forges pistons here. Wiseco has been forging pistons in the U.S. for decades and has spent countless hours on research and development to make their forged pistons the option that best combines performance and wear resistance. Still, there is a lifespan to a piston, and the above tips should be used to practice regular maintenance on your machine.
  14. Wiseco's new Garage Buddy engine rebuild kits offer everything you need for a bottom and top end rebuild. From the crank to the piston kit, and even an hour meter to track maintenance, everything is included in one box. Here we take a look at the components included, and the technology behind them. So, the time has come for an engine rebuild. Hopefully it’s being done as a practice of proper maintenance, but for many it will be because of an engine failure. Whether the bottom end, top end, or both went out, the first step is to disassemble and inspect. After determining any damage done to engine cases or the cylinder, and arranging for those to be repaired/replaced, you’re faced with choosing what internal engine components to buy, where to get them, and how much the costs are going to add up. A full engine rebuild is a serious job and requires a lot of parts to be replaced, especially in four-strokes. You have to think of bottom end bearings and seals, a crankshaft assembly, piston, rings, clips, wristpin, and the plethora of gaskets required for reassembly. If you’re doing this rebuild yourself, or having your local shop do the labor, chances are you don’t have a factory team budget to spend on parts. However, you know you want high-quality and durable parts, because you don’t want to find yourself doing this again anytime soon. Rebuilding a dirt bike engine is an involved job, requiring many parts to be replaced. Missing one seal or gasket can put the whole rebuild on hold. You could source all the different parts you need from different vendors to find the best combination of quality and affordability. But, it can get frustrating when 6 different packages are coming from 6 different vendors at different times, and each one relies on the next for you to complete your rebuild. Wiseco is one of the manufacturers that has been offering top end kits (including piston, rings, clips, gaskets, and seals) all in one box, under one part number for many years. Complete bottom end rebuild kits are also available from Wiseco, with all necessary parts under one part number. So, it seemed like a no brainer to combine the top and bottom end kits, and throw in a couple extra goodies to make your complete engine rebuild in your garage as hassle free as possible. Top-end piston kits and bottom-end kits come together to create Wiseco Garage Buddy rebuild kits. Wiseco Garage Buddy kits are exactly as the name implies, the buddy you want to have in your garage that has everything ready to go for your engine rebuild. Garage Buddy engine rebuild kits come with all parts needed to rebuild the bottom and top end, plus an hour meter—with a Garage Buddy specific decal—to track critical maintenance intervals and identify your rebuild as a Garage Buddy rebuild. The kits include: Crankshaft assembly OEM quality main bearings All engine gaskets, seals, and O-rings Wiseco standard series forged piston kit (piston, ring(s), pin, clips) Small end bearing (for two-strokes) Cam chain (for four-strokes) Hour meter with mounting bracket and hour meter decal Open up a Garage Buddy kit, and you'll find all the components you need to rebuild your bottom and top end. 2-stroke and 4-stroke Whether your machine of choice is a 2-stroke or a 4-stroke, Wiseco can help you with your rebuild. 2-stroke Wiseco Garage Buddy kits include everything listed above, featuring a Wiseco forged Pro-Lite piston kit. You don’t even have to worry about sourcing a small-end bearing, that’s included too. 2-stroke fans often brag about the ability to rebuild their bikes so much cheaper than their 4-stroke counterparts, and they’ll have even more ammo for bragging now with these kits starting in the $400 range. A Wiseco 2-stroke Garage Buddy kit includes all the parts you'll need for piston and crankshaft replacement, plus an hour meter to track your next maintenance intervals. However, don’t abandon your 4-stroke yet. Many riders cringe—and rightfully so—at the thought of rebuilding their 4-stroke because of the costs associated, but Wiseco 4-stroke Garage Buddy kits starting in the $600s takes a lot of sting off your rebuild project. They even include a new timing chain. No matter what you’re rebuilding, you’ll be able to track key maintenance intervals for your fresh engine with the Wiseco hour meter and log book that’s included in the Garage Buddy kits. All Garage Buddy kits include a specific hour meter decal as well, which is important for the limited warranty to identify the rebuild as a Garage Buddy rebuild. A Wiseco 4-stroke Garage Buddy kit includes all the parts you'll need for piston and crankshaft replacement, including a cam chain and an hour meter. Ease of ordering Wiseco Garage Buddy kits come with the listed parts boxed up in one box, and listed under one part number, which makes it nice to not have to worry about if you might’ve missed something when ordering. Simply find the single part number for your model, order, and you’re on your way to brand new performance. Quality Performance, backed by a Limited Warranty Ordering convenience doesn’t make a difference if the parts do not provide quality and reliability. Wiseco crankshafts are designed completely by in-house engineers, who determine all assembled dimensions, clearances, materials, and specifications. These specifications have been determined from R&D tests such as hand inspection, dyno, and failure analysis. Once Wiseco cranks have been manufactured to exact specifications they are batch inspected, and critical tolerances and dimensions are measured. Major inspections and tests include crank run-out and trueness, because they must operate within a strict tolerance to last long and perform well. Wiseco crankshafts and bearings are manufactured and tested according to strict tolerances and clearances, including run-out and trueness. Crankshaft designs are also tested for 4 hours at WOT. Bearings are another critical point of inspection. Wiseco has worked to build relationships with top-tier bearing suppliers to provide a long lasting, low-friction product. Debris in a bearing can lead to very fast wear, and Wiseco makes it a point to inspect batches of bearings for cleanliness and proper operation. As part of the design and engineering process, prototype crankshafts are hand inspected and dyno-tested at wide open throttle for 4 consecutive hours. This is a benchmark test, and new crankshaft designs must pass it before to be deemed worthy for manufacturing. Watch our crank R&D and inspection process. A Warranty on Engine Internals? Yes! Wiseco is committed to providing performance and reliability in all their products. This is why Garage Buddy kits come with a limited warranty. Rebuild your engine with a Garage Buddy kit, and your new Wiseco components are covered against manufacturer defects for 90 days from the date of purchase, or 10 hours logged on the hour meter, whichever comes first. Check out all the warranty details on the detail sheet in your new Garage Buddy kit. Open up your Garage Buddy kit and you'll find a detail sheet on the warranty on your new components. Forged Pistons The top end kits included in Garage Buddy kits feature a Wiseco forged piston, which are designed, forged, and machined completely in-house in the U.S.A. Four-stroke Garage Buddy kits come with a Wiseco standard forged piston, which offers stock compression and more reliability and longevity, thanks to the benefits of the forging process. Two-stroke Garage Buddy kits include a Wiseco Pro-Lite forged piston, which is the two-stroke piston that has been providing two-stroke riders quality and reliability for decades. Some applications, two and four-stroke, even feature ArmorGlide skirt coating, reducing friction and wear for the life of the piston. Forged aluminum has an undeniable advantage in strength over cast pistons, thanks to the high tensile strength qualities of aluminum with aligned grain flow. Read more about our forging process here, and get all the details on our coatings here. All Wiseco pistons are forged in-house from aluminum. Some pistons may also come with ArmorGlide skirt coating, and some 2-stroke pistons may already have exhaust bridge lubrication holes pre-drilled. All pistons are machined on state-of-the-art CNC machine equipment, then hand finished and inspected for quality. The forged pistons come complete with wrist pin, clips, and high-performance ring(s). Lastly, all gaskets and seals are made by OEM quality manufactures. Sealing components are not something to ever go cheap on, because no matter how high-quality your moving components are, if your engine is not sealing properly, it’s coming back apart. Need some tips on breaking in your fresh engine? Check this out. Gaskets and seals provided in Wiseco Garage Buddy kits are OEM quality, ensuring your freshly rebuilt engine is properly sealed.
  15. So I'm rebuilding a 4 stroke for the 1st time, I'm used to 2 strokes where they have 1 ring and a mark to line the ring up with. My 1996 ktm 400 has 3 rings and the top 2 don't have spots like my 2 stroke and then there's a 3rd ring with a spring. I just need to know where to position each ring, I checked the service manual and it just mentions how to install the circlips...
  16. New to thumpertalk! I recently got back into riding and picked up a 2012 Suzuki RMz250 (one bad mofo) and love it but ran into a snag. It was running great on my last ride when all the sudden it bogged out, after then the kick start was seized and I couldn’t get the bike to start. My uncle said it could either be the piston rings and I’ll just need a top end rebuild or it’s a dropped valve but would either of those cause the kick start to seize?? I plan on taking it apart sometime in the next week or so, if I have any time to that is, but I’m wondering what else it could possibly be or what to look/check for. Any help would be great!! By the way does anyone know where I can get a manual for this bike?
  17. Rebuilt my 2015 ktm 250 sx, new crank,piston,bearings,seals,etc. Test rode and it has 1st gear and fifth gear but 2nd,3rd,and 4th is like it's in neutral. Any thoughts before I tear it down again? I'm wondering if it's the shift drum because I kept both shafts in the same sequence when I removed.
  18. Hey I can't seem to find an aftermarket crank for my 2016 300XC. For some reason wiseco and prox don't make them. Are there any options other than stock? Thanks
  19. Hey guys, My buddy and I just finished rebuilding his 1998 CR250 which we bought with a broken connecting rod. We replaced the main bearings, crank, gaskets, seals, piston, and the cylinder bored and honed to match the new piston. I did a compression test before it ever started and read about 150 PSI. Then we started it. Ran well, but wanted to die whenever we hit the powerband (this is after we let it idle to break in the seals for twenty minutes) anyway it died a couple times always started right back up until it didn't. I did another compression test and got about 90 PSI. I refuse to believe the rings are stuck, but I guess it is possible. I took the head off and the piston looks fine. Oh also we found some small beads of coolant around the head. I ordered another head gasket (OEM) since I read that the tusk head gaskets don't work great. That won't be here until next week so I thought I'd ask you guys if I'm on the right track in the meantime. Thanks.
  20. I recently rebuilt top and bottom end. Heat cycled it, break in, ran fine. First ride, an hour in, it died and would not start again. Lost almost all compression. Has 15 psi on compression test. I have cylinder pulled off, piston and ring looks fine. Head gasket looks fine. Tightend head studs, they were a little loose. Head doesn't seem to be warped at all. I'm at a loss. Any ideas would be appreciated.
  21. Hello all, Thanks to Thumpertalk I dared to plunge into the deep and do a rebuild of the top-end of my 2012 YZ250 myself. 10hrs and still going strong. But the reason I did the rebuild (other than that the time has come), was that there was also another issue that I was hoping to fix. I'll walk you through the symptoms: Start up of the bike (cold) in cold or hot weather w choke. (PS: I think the problem is a little better in cold weather) Bike starts up in one kick if kicked correctly. The bike smokes, but normal amount to a 2stroke. After a 10 or so seconds, when I blip the throttle, ALOT of smoke comes from the exhaust (white smoke). It also doesn't ping but bogs (bwaaa) when I go on the throttle. Sometimes its so severe that it dies during the bog. When I start my ride on the track, the bike doesn't ping and I don't have much power + still excessive smoke. But when I hold the throttle WIDE OPEN for 10 or so seconds, then it starts to 'clear out' and begins to haul *ss. The smoke also disappears and the engine starts to ping again. The bike runs fine after that while its cleared out on the track. I thought this was a sign that I should change the top end (30hrs, novice) and clean the carburetor. What did I do: Completely clean and dissasembly the carburetors and jets. Change the piston, rings, gaskets,.... Replace spark plug. The problem seemed to be gone the first time that I started the bike after the rebuild (first kick yeahah!). But it quickly came back and is even identical to before the rebuild. Now I thought the cause is the following: Crankshaft seal leak at the clutch side. --> But I just checked my transmission fluid after 4-6hrs of riding and it's 650cm³ after the 750cm² I filled it with. That seems to be about normal consumption, no? Coolant leakage somewhere inside the combustion chamber --> Triple checked: not losing coolant. The following suspects: Float height Crankseal leakage Pilot jet wrong (I checked that the standard one is installed). I'm at a dead-end here. I don't have the friends with the knowledge to ask these questions to. But I'm laying my faith in the hands of thumpertalk :). If there is something I can do to test something for you guys, let met know. Kind regards, Dries This is the me, my bike and the issue (it got a bit worse over time :p). Yes I know I shouldn't be so hard on the throttle when I start it, but for one time its not bad and it was necessary to show the problem.
  22. First post. Been lurking for a while here. My first 4 stroke, rode two strokes all my life. Ive had this bike since new in 15 and trail rode it pretty hard the last few years, always kept up maintaining filter and oil and valve checks. Well i was in a hurry and managed to put the oil filter in backwards one morning and after developing a loud knock i had it in the shop, they scoped it and the tech said theres was definitely some scoring on the cylinder wall and there might be some play in the rod bearing. I decided to just take it home and take it apart myself. I got the head off and im currently waiting for a flywheel puller that i ordered so i can finish taking the cylinder out. From what i can see with the piston down, the cylinder looks fine to me. I dont see or feel and chips, scratches, scoring none of it. I can see the original cross hatching or honing marks in it but nothing I would consider damaged. Im gonna take the cylinder into a couple shops and see what they say about it. So I have a few questions for you guys. 1. How can i check the rod bearing without splitting cases. Simple as pushing on the rod to see if theres any play there? 2. I 99% trail ride the bike, wanting to start racing our local GP series and maybe a hare scramble or something like that. Are there any parts you guys recommend i put in there while its apart? Heavier flywheel, different gearing? anything like that? From what ive been seeing a lot of the aftermarket parts are barely any more $$ than OEM and if it tames the 450 a little for the woods thats a huge plus for me. 3. I cant find any information on getting the cases back together after doing the repairs, they just bolt back together? Crank needs to be pressed back in? I dont have to do the old oven freezer bullshit do i? Bike is bone stock right now. Im also looking for suggestions on pistons and rings. Currently looking at either OEM or cylinder works. Thanks in advance if anyone can help a brotha out
  23. Hi this is my first time here and I was wondering if a lt80 cylinder would fit on a ds80 bottom end. I cant find a new ds80 cylinder for cheap but I can find a cheap top end rebuild kit for a lt80 and the cylinder sizes are close.
  24. Im rebuilding my 2000 drz's lower. It didnt have many miles on it aka 1500, but my crankshaft bearing is out and i need to replace it amd dont have the tools to change just the bearing. I was curious what brand yall would recommend the hotrods ive heard good and bad mixes. Please if you've replaced a crankshaft or know a reliable brand let me know. Thank you for your time. A.C. DrzFlorencybell
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