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Found 164 results

  1. gunnar127

    Yamaha YZ125 (2005)

    0 comments

    Fast,nimble,light weight machine.
  2. xr250r_Project

    Boring over Xr250r

    I am trying to bore over my dirtbike. I had someone take it apart to put rings and gaskets in it but they showed me that i needed a piston. So i ordered a piston. My original piston was a 73mm my new one is a 73.50mm. will this piston work?? And can i bore it myself because the guy i had doing it i dont believe is doing it anymore. Also is there anything other than the cylinder that needs to be messed with?? Thanks in Advance
  3. ThumperTalk

    Wiseco Piston Kit

    20 reviews

    Forged from high-silicon aluminum alloy for maximum strength and dependability Wiseco offers a complete range of popular piston models and years for both trail and racing applications Durability, longevity and increased horsepower Innovative forging design and piston skirt provide maximum horsepower and torque All Wiseco High-Performance Motorcycle Pistons come with rings and circlips
  4. FORCON8541

    Kawasaki KDX200 (2006)

    0 comments

    Awesome Bike to have around. Great in the trails and small MX tracks. Reminds me of mid 90's KX125
  5. Rb26sx

    Suzuki RMZ250 (2007)

    0 comments

    Its great. out of the box the suspension was spot on, bikes feels great
  6. Jake Rose

    Honda CR250R (1998)

    0 comments

    Badass bike just rips!
  7. yzS50f

    Yamaha YZ250F (2007)

    0 comments

    Plenty of power, great range, great suspension. Engine design is decent, carb is okay. First Engine blew up, had to get an entirely new used one. New engine/shining not shown in pic.
  8. arinlee22sr

    Suzuki RM65 (2003)

    0 comments

    Very fun bike, tiny but fun to mess around on.
  9. Ok guys I have a problem... I'm sitting here on my computer in the middle of winter WONDER! WHY! I cant seem to finish my yz125 project It goes like dis: I replaced the bikes worn sleeve (its a 2001 but it has a sleeve) and bottom end CASE bearings, then a fresh wisco goes in, stranded bore. The thing rides for maybe a few hours and starts to tick AWFUL, so i pulled it apart and check this out: *notice the sizable lip up top there* the piston the rings looks thin in one spot???? after further inspection I concluded it was a bad crank (i should have replaced when i did the case bearings .-.) NO PROBLEM.... SO! new crank fresh bore fresh crosshatch fresh top end kit and i SWEAR the ticking is back and loud as ever, with in 20 minuets of riding so my question is: WHAT AM I DOING WRONG!?!?!?!??!?! installation, assemble, break in, im following all the instructions and specification. this isnt the first bike I've rebuilt, but I never!! anyway any help would be GREATLY appreciated
  10. ThumperTalk

    WSM Complete Piston Kit

    1 review

    Quality and construction that meet or exceed OEM Feature improved E-clip design Kits contain piston, rings, pin and clips Rings available separately
  11. SaxtonGoesBraap

    Boyesen Porting Polishing

    2 reviews

    GENERAL INFORMATION One piece design Easy installation The intake charge is redirected for more even distribution to the intake ports Porting the cylinder head
  12. KJ790

    Changing a 4-Stroke Piston

    So today I decided to throw a new piston (high compression of course) in my 250F. Many people are afraid of getting into an engine at all, but it really isn't very hard as long as you take your time and make sure everything is clean. First thing you need to do is wash your bike, and wash it well. No matter how well you wash it, there will be a lot of dirt still on it when you start taking stuff off. The goal is to get every area around the engine spotless. You don't want any dirt falling into your engine while it's open! Once you remove the pipe, gas tank, shrouds, and head stay you will most likely find a lot of dirt on top of the valve cover and on the frame. In this picture you can see what I'm talking about. The valve cover is covered with dirt still. I like to use a shop vac and a small screw driver to pick at the dirt and suck it away (so it doesn't just fall somewhere else on the bike. You once the chunks are cleaned up you can use a damp cloth to get it spotless. Don't remove anything else until the frame and valve cover are spotless. Next you can drain the water out of the radiators and remove the radiator hose that goes to the head. Next you can go ahead and remove the valve cover. At this point you can get out a feeler guage and check the valve clearances if you want. Next I loosened the clamp between the carb and the head, then removed the top bolt on the subframe while loosening the other two bolts that hold the subframe to the frame. This allows you to tilt the subframe back, pulling the carb out of the way. Remember, my goal is to remove the least amount I have to. If you want to completely remove the subframe and the carb, go right ahead. On many bikes, the hose connecting the two radiators is very close to the head. To deal with this I removed the bottom bolts on the radiators and loosened the top ones, then just rotated the radiators forwards: Next, tie a piece of wire around the cam chain to make sure that it doesn't fall down into the bottom end when you remove the cams. Unbolt any oil lines going to the head. Remove the cam chain tensioner. Before you remove the cams, cover the area where the cam chain runs through with a rag so that the cam clips cannot fall down in it should they fly out as they often do. Now you can remove the cams and unbolt the head. Next you can unbolt the cylinder and pull it up allowing the piston to slide down out of it. Cover the crank area around the rod with a clean rag or paper towel to keep anything from falling in there (such as dirt or wrist pin clips). Next, remove one c-clip and slide the wrist pin out to remove the piston. Clean all gasket surfaces, hone the cylinder, measure everything and make sure that all of the measurements are within spec (given in the owner's manual). Once you make sure everything is in spec, you can put one c-clip in the new piston. Make sure it fits in the grove completely. Put the new rings on the new piston, making sure the gaps are aligned as your manual shows (normally opposite sides of the piston from each other). Put the piston on the rod and slide the new wrist pin through, make sure to coat the wrist pin in oil before putting it in. Make sure the piston is in the correct way (most have a mark showing the front side). Then install the second c-clip. Make sure that it fits all the way into the groove. this is very important, if the c-clip falls out while the engine is running it will cost you a lot of money. Make sure both c-clips have their openings facing down. Install a new base gasket. Now you can slide the cylinder over the piston, using one hand to squeeze the rings together. Make sure the rings stay in their correct grooves. Use a torque wrench to install all bolts according to the owner's manual specifications. Now you can put on a new head gasket and put the head back on. Make sure the engine is at top dead center (marked on the flywheel) and put the cams in. Make sure that the marks on the cams are in the correct places for the engine at top dead center (your manual will show you what to look for). On my bike each cam gear has a dot that should be horizontal and flush with the top of the head. Install the cam chain tightener and double check the timing. Many people neglect to do this and have problems. When the tensioner is installed, it often rotates the intake cam backwards, revealing that the intake timing is off one tooth. If this is te case, take the tensioner back out, remove the cam cap and turn the cam to the correct timing. Now you can put the valve cover back on and reinstall any oil lines. Be careful with banjo joints. In my case the banjo bolt couldn't hold the torque recommended by the manufacturer These do not need to be very tight, just enough that they won't leak. Obviously mine was too weak to hold the torque that Yamaha recommended, so the new one was put in using less torque to be sure that I wouldn't have that problem again. Reinstall the headstay, radiator hose, and radiators. You can now pull the subframe back and reconnect the carb to the head. Fill the radiators and put on the exhaust and plastic and you are now ready to break in your fresh top end.
  13. brianhare

    Honda XR650L (2001)

    0 comments

    The bike is under powered,but can be improved upon by engine mofifications....a Kehin FCR MX definately wakes up the performance..
  14. Will I Am

    CR125 High Revving on Start Up

    So, I've had this problem/question for a while now and have never been able to get a definite answer. Some people have told me it's normal, others have said otherwise. When I cold start my 2006 cr125, the bike revs up pretty high before dropping to normal idle (once the engine is warm it starts up fine). It does this whether the choke is on or off, but is much worse with the choke on (I always turn the choke off as soon as the bike fires but the result is still worse). It revs to the point where, if I start it on the stand in first gear, I don't have to hold in the clutch when I kick it over and the rear wheel starts spinning like crazy. I've adjusted the throttle free play, the float height, everything I can think of. I doubt it's an air leak because it runs fine once it calms down. I read somewhere that a worn top end can cause this? My bike is ready for a top end rebuild but I've been holding off because I worry that with a new piston and the bike revving up like this on its first start, recipe for disaster. Thanks in advance for any advice you can give me, maybe it is just normal for this bike but it doesn't feel normal and I'm out of ideas. Thanks, Will
  15. 2 stroke top end - never done one. Is it this simple? Do I have this right? Gonna use all/only OEM parts. 1. Remove head, cylinder, (use pin for power valve) and piston from connecting rod and check connecting rod for free play. 2. Check marks on cylinder and piston - in this case a "B" is marked on the side of the cylinder. 3. Mic cylinder as per manual. If it's good, buy new B piston, piston pin, small end bearing, circlip, gaskets, etc. 4. If it's not good buy a matched set of piston and cylinder - and all the other parts. Not sure how I buy a "matched set." Just tell the parts house? Where does replating the cylinder come in to play? I'll assume it's more cost effective than buying a new cylinder. Thanks.
  16. ThumperTalk

    Athena GET Piston Kit

    2 reviews

    Forged All pistons are moly coated to help during critical break in period The only forged piston that offers A, B, C sizes for Nikosol cylinders, Compression Standard
  17. Crack in piston. Has to change piston and sylinder. Wondered if anyone knows ho much play theres suppose to be on the rod bearing? Sideways i mean. So i know if i have to change the bearing, or if it`s enough to just change te piston and sylinder Btw, all new to the forum so show mercy Is it normal thet the piston just cracks up like this? I have only driven the bike for about 30km.. Adding a link to show what i mean.
  18. Kurt2296

    2001 RM250 cylinder scores!

    Hey guys, First time poster on Thumpertalk, thought id give it a go and see what you guys have to say since I'm fairly new to engine work. Anyways - I'm rebuilding my 2001 rm 250's top end and when i pulled off the top end from the bike i noticed some score marks along the side of the cylinder and on the piston. On the piston side the scores were pretty bad, you could easily feel it let alone see it. But on the cylinder side it really wasn't terrible. More visual than anything you could feel - maybe one small mark that i could feel and that's about it. Ill post some pictures in a couple of hours but basically I'm just curious as to whether you guys think that a simple hone will fix it up or am i in for a big bill? I live 10 mins away from Bondi engines in Ontario so i lucked out there. Likely going to see what they can do for me on Monday after work. Any input would be greatly appreciated!
  19. I recently went through my cr80 and found out almost every reason why the cr80 motor might not be functioning correctly. I made a youtube video about this and i encourage you to watch it if you have problems with your bike...plz leave feedback. video is in link above, enjoy and subscribe
  20. Whether you're racing or looking for increased performance out on the trail, there are a plethora of performance upgrades to consider to increase the power of your machine. Piston manufacturers like JE Pistons offer high compression piston options for many applications, but there are important merits and drawbacks you should consider when deciding if a high compression piston is right for your application. To better understand, we’ll take a look at what increasing compression ratio does, what effects this has on the engine, detail how high compression pistons are made, and provide a high-level overview of which applications may benefit from utilizing a high compression piston. Bumping up the compression in your motor should be an informed decision. It's important to first understand what effects high-compression has, the anatomy of a high-comp piston, and what applications typically benefit most. Let’s start with a quick review of what the compression ratio is, then we’ll get into how it affects performance. The compression ratio compares the volume above the piston at bottom dead center (BDC) to the volume above the piston at top dead center (TDC). Shown below is the mathematical equation that defines compression ratio: The swept volume is the volume that the piston displaces as it moves through its stroke. The clearance volume is the volume of the combustion chamber when the piston is at top dead center (TDC). There are multiple different dimensions to take into account when calculating clearance volume, but for the sake of keeping this introductory, this is the formula as an overview. When alterations to the compression ratio are made, the clearance volume is reduced, resulting in a higher ratio. Reductions in clearance volume are typically achieved by modifying the geometry of the piston crown so that it occupies more combustion chamber space. Swept volume is the volume displaced as the piston moves through the stroke, and clearance volume is the volume of the combustion chamber with the piston at top dead center. How does an increased compression ratio affect engine performance? To understand how increasing the compression ratio affects performance, we have to start with understanding what happens to the fuel/air mixture on the compression stroke. During the compression stroke, the fuel/air mixture is compressed, and due to thermodynamic laws, the compressed mixture increases in temperature and pressure. Comparatively, increasing the compression ratio over that of a stock ratio, the fuel/air mixture is compressed more, resulting in increased temperature and pressure before the combustion event. The resulting power that can be extracted from the combustion event is heavily dependent on the temperature and pressure of the fuel/air mixture prior to combustion. The temperature and pressure of the mixture before combustion influences the peak cylinder pressure during combustion, as well as the peak in-cylinder temperature. For thermodynamic reasons, increases in peak cylinder pressure and temperature during combustion will result in increased mechanical efficiency, the extraction of more work, and increased power during the power stroke. In summary, the more the fuel/air mixture can be compressed before combustion, the more energy can be extracted from it. Higher compression allows for a larger amount of fuel/air mixture to be successfully combusted, ultimately resulting in more power produced during the power stroke. However, there are limits to how much the mixture can be compressed prior to combustion. If the temperature of the mixture increases too much before the firing of the spark plug, the mixture can auto ignite, which is often referred to as pre-ignition. Another detrimental combustion condition that can also occur is called detonation. Detonation occurs when end gases spontaneously ignite after the spark plug fires. Both conditions put severe mechanical stress on the engine because cylinder pressures far exceed what the engine was designed for, which can damage top end components and negatively affect performance. Detonation and pre-ignition can spike cylinder pressure and temperature, causing damage. Common signs of these conditions include pitting on the piston crown. Now that there is an understanding of what changes occur during the combustion event to deliver increased power, we can look at what other effects these changes have on the engine. Since cylinder pressure is increased, more stress is put on the engine. The amount of additional stress that is introduced is largely dependent on the overall engine setup. Since combustion temperatures increase with increased compression ratio, the engine must also dissipate more heat. If not adequately managed, increased temperatures can reduce the lifespan of top-end components. JE's EN plating is a surface treatment that can protect the piston crown and ring grooves from potential damage caused by high cylinder pressure and temperature. EN can be an asset for longevity in a high-compression race build. Often, additional modifications can be made to help mitigate the side effects of increasing the compression ratio. To help reduce the risk of pre-ignition and detonation, using a fuel with a higher octane rating can be advantageous. Altering the combustion event by increasing the amount of fuel (richening the mixture) and changing the ignition timing can also help. Cooling system improvement can be an effective way to combat the additional heat generated by the combustion event. Selecting larger or more efficient radiators, oil coolers, and water pumps are all options that can be explored. Equipping the engine with a high-performance clutch can help reduce clutch slip and wear which can occur due to the increased power. High-level race team machines are great examples of additional modifications made to compensate for increased stress race engines encounter. Mods include things like larger radiators, race fuel, custom mapping, and performance clutch components. Let’s take a quick look at what considerations are made when designing a high compression piston. Typically, high compression pistons are made by adding dome volume to the piston crown, which reduces the clearance volume at TDC. In some cases, this is difficult to do depending on the combustion chamber shape, size of the valves, or the amount of valve lift. When designing the dome, it is essential to opt for smooth dome designs. Smooth domes as opposed to more aggressively ridged designs are preferred because the latter can result in hot spots on the piston crown, which can lead to pre-ignition. Another common design option is to increase the compression distance, which is the distance from the center of the wrist pin bore to the crown of the piston. In this approach, the squish clearance, which is the clearance between the piston and head, is reduced. Higher compression is commonly achieved by increasing dome volume while retaining smooth characteristics, as pictured here with raised features and deep valve pockets. Compression height can also be increased, which increases the distance between the center of the pin bore and the crown of the piston. A high-level overview of which applications can benefit from increased compression ratio can be helpful when assessing whether a high-compression upgrade is a good choice for your machine. Since increasing the compression ratio increases power and heat output, applications that benefit from the additional power and can cope with additional heat realize the most significant performance gains. Contrarily, applications where the bike is ridden at low speed, in tight conditions, or with lots of clutch use can be negatively impacted by incorporating a high compression piston. Keep in mind these statements are generalizations, and every engine responds differently to increased compression ratios. Below are lists of applications that may benefit from increasing the compression ratio as well as applications where increased compression may negatively influence performance. Applications that may benefit from utilizing a high compression piston: Motocross Supermoto Drag racing Road racing Ice racing Flat track Desert racing Motocross and less technical off-road racing are two of multiple forms of racing in which high-compression pistons can benefit performance due to higher speeds and better air flow to keep the engine cool. Peick photo by Brown Dog Wilson. Applications that may be negatively affected by utilizing a high compression piston: Technical off-road/woods riding Trials Other low speed/cooling applications Lower speed racing and riding may not benefit as much from a high-compression piston, as heat in the engine will build up quicker due to lessened cooling ability. Fortunately, if you’re considering increasing your engine’s compression ratio by utilizing a high compression piston, many aftermarket designs have been tested and optimized for specific engines and fuel octane ratings. For example, JE Pistons offers pistons at incrementally increased compression ratios so that you can incorporate a setup that works best for you. For example, high-compression pistons from JE for off-road bikes and ATVs are commonly available in 0.5 compression ratio increases. Assume an engines stock compression ratio is 13.0:1, there will most likely be options of 13.5:1 and 14.0:1, so that you can make an informed decision on how much compression will benefit you based on your machine and type of riding. From left to right are 13.0:1, 13.5:1, and 14.0:1 compression ratio pistons, all for a YZ250F. Notice the differences in piston dome volume and design. If performance is sufficient at an engine’s stock compression ratio, there are still improvements in efficiency and durability that can be made with a forged piston. Forged pistons have a better aligned alloy grain flow than cast pistons, creating a stronger part more resistant to the stresses of engine operation. In addition to forged material, improvements can be made on piston skirt style design to increase strength over stock designs, such as with JE’s FSR designs. JE also commonly addresses dome design on stock compression pistons, employing smoothness across valve reliefs edges and other crown features to improve flame travel, decrease hot spots, and ultimately increase the engine’s efficiency. Even if stock compression is better for your application; forged construction, stronger skirt designs, and more efficient crown designs can still provide improved performance and durability. If it’s time for a new piston but you’re still not sure what compression ratio to go with, give the folks at JE a call for professional advice on your specific application.
  21. So this is what a piston looks with yamalube 2r at 40:1 with 91 octane gas. I ride harescrambles and trail ride and a little bit of motocross but the bike is usually pinned
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