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Found 146 results

  1. PRIOR INFO Hey all, before i start i want to introduce some prior info in case it helps you guys give me some feedback. I'm a south Florida sand track rider that currently rides a 2015 CRF150RB and would probably classify as a 85cc B rider. I learned to ride on this bike and I still feel it has plenty of room for me to get better on and still has plenty of power left for me to use, i usually only top out 4th gear occasionally with a 56T rear sprocket. The reason i'm considering a 125 within the next year or so is because i'm 5'7" and growing and about 130 pounds and soon i wont fit on this bike. I figured that a 125 two stroke would be perfect since i'm still able to find power with this bike and i ride sand a lot, also so i don't get lazy . ACTUAL QUESTION Currently I'm set on a CR125R because i'm just a Honda guy and from what i've heard these days if your getting a Japanese bike is pick your favorite color and ride it because most of us don't push the bikes to the limit anyway. In my area I see only 1998's 2001's and 2004's. I don't know much about the year history but i heard there were weak engines from 01-04 and the aluminum frames sucked from 99-04. You guys have any insight? The 04's look the best around here but i'm not sure they perform the best.
  2. This is the saga of my poorly maintained 2003 YZ250 that I bought about a year ago. I added a few mods last summer to help me get by then deployed to Africa for 6 months. The poor bike was riddled with SAE hardware, spray foam where there should have been gaskets, and ziptied rear fender, a horribly cut seat, and plenty of other unspeakable things. However, it came with a title and the engine did run pretty strong at the time...even though it had a hint of engine noise. Over time, the noise progressed and I knew what had to be done. While I was away, I coerced my wife into sending a used crankshaft i bought out to Mr. Crankshaft so I'd have a spare for a quick swap... This is it after I replaced the fuel tank that had a split in it and put a lectron carb on. It still wasn't that smooth and the wheel/tire combination were unforgiving, plus, the suspension and rebound were set for a wanna-be-freestyle MX rider. This is the transition to where it was before I really dove in GT216AA Front with Nitro Mousse 18" Rear with Shinko 505 Cheater rear and Nitro Mousse Low Enduro bend Flexx bars (eventually putting steering dampener on) SSS Forks and suspension done by W.E.R. DEP Armored Enduro Pipe Steahly 9oz Flywheel Weight Devol Skidplate IMS/Zipty tank Non-cracked white rear fender Tall seat...I forget who made it, but it does what it do and fits well. Head cut by 218 (head was cut after this photo was taken) rock kickstand During this ride, I had next to no bottom end due to a stuck powervalve. This was my first ride since I came home. I never really tore into the engine, so I got in there, cleaned it up and replaced a broken powervalve pulley and a few areas where parts were missing from the previous owner(s). Two weeks after this picture, I took it out to the mountains for the fourth of july and it started to get real nasty sounding and not in a good way This is why: While I was in there, I figured I'd send the top end out to Eric Gorr...and since that has a 2.5 week lead time, I might as well get the frame in order. Now my bike looks like this. The frame was spray bombed over who knows what, which was over the the original finish. That is being re-mediated. To be continued...
  3. KTM introduced its lastest EXC models at the iconic Erzberg in Austria. For more information visit http://www.ktm.com/enduro
  4. Hey guys, I'm new to thumper, but I was hoping I could find someone who could help me. HERES THE DEAL! I've been riding 4 strokes for about 7 years now, but the 2T world has recently gotten my attention! I currently ride a 2006 YZ250F. (Fully rebuilt by myself;). I ride the piss out of it and I feel like it's missing something. I've tried shaking things up like riding different terrain(sand dunes,Rocks,etc.) I thought maybe I would try a 450, I got to ride my buddies CRF450X. lol that bike humbled me. It was way to high and It felt a LOT heavier. I crossed out the 450 bc I think it would be a waste and I wouldn't be able to push the bike to its limits. With that being said I'm trying to decide between (2017 Ktm 150 sx, 2017 Ktm 250sx, and 2017 YZ250 and/or the X model). Here's me.. I'm roughly 5'8" 175-185lbs. I lift 5-6 days a week. I enjoy riding anything and everything as long as I get to ride.
  5. Hi, Have a Kawasaki KX250 with a ecotrons two stroke efi turbo kit. Has any one else fitted one of these kits? Having problems getting it tuned right. Starts really well and on bitimun once you get past the bogging it really flies but once on sand or dirt it runs very lean. Despite advertising turbo two stroke kits Ecotrons dont seem to know a lot about tuning the EFI to suit and auto tuning with the 02 sensor hasnt helped. i tried manually tuning but that was worse. If someone has got one to work I would like to hear from them and wouldnt mind trying their Cad file. I know it wont be perfect for my set up but it should put me in the ball park. I did ask Ecotrons toput me in touch with someone who has got one to work but they just put me in touch with their tech department.
  6. I was looking to replace the old boyesen power reeds on my 01 cr250, so I ordered some boyesen pro reeds for it. But these ones have 3 holes in the lower petals where the cage has 2 larger holes. Is there any way to make these work or should I send them back? Can I modify the cage without &%$#@!ing it all up? Sent from my SM-G900F using ThumperTalk mobile app
  7. I got a new to me 2001 yz 250 which has a healthy motor and jetted properly for my elevation. The problem I'm having is when I'm in gear riding and push in the clutch the rpms don't drop to idle but if I give it gas it doesn't slip and revs freely. I can start the bike in gear fine and looked at my clutch already which has plenty of life left and my clutch basket is in good condition to. I adjusted my clutch freeplay which was already in spec. It has aftermarket clutch lever and I maxed it out as far as it can go outwards but the rpms still wont drop to idle when im trying to coast in gear. Another weird thing is if I'm stopped in gear with clutch pulled in it is at idle speed. Any suggestions is appreciated because I don't know what else to check.
  8. I have been riding dirt bikes for a little less than a year and I always ride trails and enduro. I have a crf250x right now and want to get a two stroke to go with it, should I get a Ktm 250 mxc? Or should i go with a yz 250 or cr 250? I've heard good and bad things about all of these bikes, and I need some help making a decision. I am going to look at this bike soon: https://portland.craigslist.org/wsc/mcy/d/2000-ktm-250-mxc/6552466361.html. I don't know if it is a good deal or not. Please help.
  9. Hey all, I'm new to this forum. I bought a 2001 CR250 a couple weeks ago, and it worked great. I bought a new clutch lever off of ebay and installed it. The lever must have been a wrong one, because I no longer had any free play. The lever was clamped tight against the perch, and even after I loosened it all the way (from both adjustment points) it would not loosen up. I took it off and installed the stock lever again, but there is now almost no free play again. The hand adjusted one is almost as far as it goes, and the other one is adjusted as far as it goes. I have enough free play, but I can't loosen it out any more. Also, since putting the stock lever back on, when I try to start the bike in first gear (with the clutch lever pulled all the way in) the bike pulls forwards fairly hard. Why does it do this?? I don't get why it worked perfectly before, but now it's all wack. Any help is appreciated.
  10. I have a 2002 yz85 and when you start it up, it will idle really low then once you rev it up a little, it will start to idle normally but then after a couple seconds it just drops back down to a really low idle like its about to stall out. What could be causing this? After doing some research it sounds like it might be a crank seal leak, but i really hope not. Could it be anything else causing this? And if it is a crank seal leak, would it require splitting cases to replace? I also just cleaned out the carb and put fresh 32:1 in it.
  11. Hey, Now this topic is all over the internet and I know theres no real answer, but I just wanted to hear your opinion do think 2 stroke or 4 stroke is better and why? Thanks
  12. After doing some adjusting to my float, my 2 stroke has started running a lot better than before but started acting a little bit funny. First, It's a little bit of a pain to start. Then, The idle feels low and it dies if not given gas. Also, if I'm on the clutch while coasting it tends to die. Lastly, bottom and mid power feel pretty good, but the top end power feels weak. Whenever I stop it pours a little gas out of the vent hoses. Is my problem still my float? If so, how do I adjust to fix this?
  13. Let me start off saying I LOVE my 08 CRF450. It performs close to flawless...is in like new condition...zero complaints. So no real reason to replace it. With all the updates to the new Husky TC250 and KTM 250SX I am considering making the switch back to 2strokes. Just trying to gauge if I am just hyping myself up a bit over the new 2strokes or if it is worth considerong selling the 450 and picking up a new TC250. I mainly just ride on practice tracks for fun. I dont race serious and may run 1-2 per year. Just want to get some thoughts or if anyone already switched to a new 2stroke. I know it's a bit easy to hype yourself up when you want something.
  14. Today I want to shift gears, open the floor for discussion, and talk about the state of dirt biking as it relates to the bikes we buy, ride, and maintain. In my relatively short existence, a number of things have happened in the industry which has been interesting to see. A few examples, which are not by any means exhaustive of all that has gone on, include the emergence of the four-stroke power plant, electronic fuel injection, improved tire technology, electric bikes, and the development of air forks. On a more micro-level we’ve seen improvements to materials, new manufacturing processes, and coating processes which have allowed ever increasing performance. As a fellow rider and someone who has no bias or stake when it comes to manufacturers and product offerings, I’d like to hear your thoughts as they relate to today’s machines. My question to you is a simple one, are your needs as a consumer being met by today’s manufacturers and bikes? What aspects of today’s machines do you love and what are pain points for you? If you could do things your way, what would you change? Are there machine variants that aren’t being offered? Leave a comment below that addresses these questions or share your historical perspective! I look forward to your responses. Thanks and have a great week! - Paul https://www.diymotofix.com/
  15. This week I want to talk about two-strokes. To kick off this post I have some awesome news. The Two Stroke Dirt Bike Engine Building Handbook is off to the printers and will be available for pre-sale very soon! Getting the book off the ground has been no cake walk. It's been two years coming and we are so thankful our riders and fans have been patient with us! At the end of this post I'll give you instructions on how you can stay updated on the launch. With that said, let's get started. Today's post aims to provide an overview of the important aspects of the two-stroke cylinder and answers a couple commonly asked questions relating to cylinder modifications. The ports found within a two-stroke cylinder in combination with the exhaust system have the greatest influence on power, torque, and the RPM at which maximum power is created out of the various engine subsystems found within a two-stroke engine. Typically when a new engine is designed the port characteristics are one of the first parameters to optimize. With this being the case they are also one of the first things anyone planning on altering an existing engine should consider improving or tailoring to their specific application. A two-stroke cylinder consists of exhaust, transfer, and occasionally inlet ports (true inlet ports are only found on piston or rotary valve controlled engines). The port heights, widths, areas, directions they flow, and relationships to one another all have a significant influence on how the engine will behave. The cutaway of the cylinder shown details the port arrangement and common nomenclature. The inlet port/passage delivers air into the engine’s crankcase, most commonly through a reed valve, on a dirt bike engine. On older engines, a rotary valve or the piston may also be used to control the opening and closing of the inlet port. On modern machinery, the inlet simply connects the reed valve to the cylinder or crankcase. In this case, the primary restriction in the inlet port is the reed valve and as such the valve’s geometry and flow capabilities often dictate the inlet port's performance. The transfer ports are responsible for moving fresh air and fuel up from the crankcase into the cylinder. This occurs as the piston travels downward after the cylinder has fired. Once the piston uncovers the tops of the transfer ports the blowdown phase is complete, at which point much of the exhaust gas has been expelled from the cylinder. As the transfer ports begin to open, the exhaust pipe sucks fresh mixture up through the transfer ports into the cylinder. To a lesser extent, the downward motion of the piston also aids in creating a pressure differential between the crankcase and cylinder. The shapes and flow capabilities of the transfer ports play a big part in how effectively the cylinder can be scavenged of exhaust gases and filled with fresh air and fuel. The transfer ports also help cool the piston. The exhaust ports dictate how much and how well exhaust gases depart the cylinder. Similar to the transfer ports, the duct shape, angle, length and volume have a large influence on how well gases can flow through the port. Typically, dirt bike engines commonly feature bridge port or triple port designs. General insights into a cylinder’s performance can be made by characterizing attributes such as the timing of the exhaust and transfer ports, the port widths, and the directional flow angles, but a deeper analysis is required to truly optimize a cylinder. Today, tuners and designers rely on computer software which computes a port’s specific time area (STA). As defined in the EngMod 2T software suite, “STA provides an indication of the effective port window area that has to be open for a certain length of time to allow enough gas to flow through the port to achieve the target power at the target RPM for the given engine capacity”. STA values are used to quantify the exhaust, transfer, and inlet port geometry as well as the blowdown phase of the two-stroke cycle. The blowdown phase occurs between exhaust port opening and transfer port opening and is one of the most important parameters in predicting engine performance. By manipulating STA values and subsequently the height, shape, and size of the exhaust, transfer, and intake ports, an engine’s power characteristics can drastically be altered. Port modifications can be made which allow more air to move through the cylinder, ultimately increasing the power of the engine. Conversely, ports can be filled or welded and reshaped which tame the engine and provide less peak power but a broader spread of power. Simple modifications to the ports can also be carried out which improves the air or exhaust gas flow through the port yielding better cylinder scavenging. Can I modify my own cylinders? Unless you have a deep passion for two-stroke tuning, are willing to spend money on software and porting equipment, and are comfortable throwing away botched cylinders, I would recommend having a reputable professional carry out any desired port modifications. Experienced tuners have developed a number of porting combinations that will work well for various makes/models and riding applications which will take the guesswork out of the situation and provide you with a good performing cylinder. Who should consider two-stroke porting modifications? For the sake of simplicity, I will lump porting modifications into two categories: major and minor. Major port modifications would include tasks such as significantly changing the port timings (by either removing or adding material), altering the shapes of the ports, or changing the directions the ports flow. Anyone drastically altering their engine, such as turning an MX engine into a road racing engine, should consider major porting modifications. Other examples of applications that may require or benefit from major port modifications include drag racing, hare scrambles, ice racing, or desert racing. Minor port modifications would include basic tasks such as removing casting flash, slightly altering the ports to achieve the stock port timing, and correcting areas that result in minor flow deficiencies. Just about everyone could benefit from these types of corrective actions; however, if the engine is already performing or producing adequate power, they often aren't considered. I hope you enjoyed this writeup on key features affecting the performance of two-stroke cylinders. To stay officially updated on The Two Stroke Dirt Bike Engine Building Handbook we created an email sign up for our readers. Click this link to see the new cover, the Table of Contents, and some sneak peek pages right from the book. Thanks for reading and have a great rest of your week! -Paul
  16. Does any body have any tips on how to make sure that may shifting assembly works before I put my yz85 engine back together? I would like to make sure it works before so that I don’t get the engine back together and find out that a I put something together wrong. I want to make sure that it goes through all the gears and into neutral how do it do this?
  17. So there are a couple of spots on the frame of my yz85 where the paint has been worn away. I was wondering if any body knows if there is any rather cheap rattle can paint that could at least closely match the stock metallic blue color?
  18. So as I’ve been saving up for parts for my yz85 my mind has obviously been on riding a lot. I’ve watched videos of people riding these two stroke bikes, but they never seem to help because they are never doing the same type of riding as me. I am going to ride corn fields (when they’re plowed) and trails with this bike. Right now I want to talk about riding in the fields. On the videos I’ve watched the people riding just go wide open, highest gear pegged when they are riding in a straight line, which is mostly what I do in fields. That is great and when I’m riding in my own I will probably do some of this. The only issue is is that most of the time when I’m riding, I am doing it with my two friends who ride a TT-r 125 and a Polaris 570. Both are decently fast machines but when I’m riding with them we aren’t a going high gear pegged the whole time and they can’t keep up with the yz85 and I don’t want to just leave them in the dust the whole time. My first when I ride is to go full throttle and get up to probably about third gear and then ride that gear at mid range rpm’s and hit the power band every once in while to get a fun little boost of speed so that I can keep a good pace with my riding buddies. My second strategy would be to go full throttle and get up to third or fourth gear and then cruise with little bits of throttle and hitting the power band to keep speed up but not go too fast Which way of riding sounds better to you guys!!?? THE REST OF THIS WRITING IS NOT A PART OF THE QUESTION, JUST BACK STORY: (I know people are going to tell me I don’t need a two stroke race bike to ride in the fields and I know that but I just got this bike because it is my dream bike (not a blown up yz85 like mine) and I have always wanted to ride a two stroke because they look fun. I am just worried I’m going to put all this money into fixing my bike and then ride it wrong and mess it up again. Trust my neither me or my dad has the money to spend on me destroying this bike if I mess it up again. We bough this bike not knowing that is had bottom end issues and I figured that out the hard way after riding it for less than an hour and the connecting rod bearings going out. It is going to take me al summer to save up for new parts and I don’t want to save up for them again!)
  19. So I went to change the oil on my 2005 yz85. Obviously you put two stroke oil in the gas. As far as the oil you drain out of the bottom of the bike with the drain screw, that is gear oil right? I have some yamalube 10w-40 engine oil and I shouldn’t replace the old oil with engine oil right. Shouldn’t I put gear oil in? Basically, should I put engine oil or gear oil in the bike when changing the oil?
  20. So I recently bought a used 2005 Yamaha Yz85. The bike is generally in pretty good condition; a few things missing here and there, but nothing that isn’t expected on a used two stroke. One thing though is an issue: the forks. The forks are very hard and barely move a lot of the time. When they do move, they go down with a lot of resistance, but then get stuck were they were pushed to and very slowly come about half way back up. When you push them down they leave a little ring of residue where they stopped. Do the fork seals need replaced, does it need new fork oil, or is it something more serious? Any info is appreciated.👍
  21. Hi all I have a ktm 300 exc 2017, didn’t make any mods, and run it about 20 hours. Last two rides I noticed a knocking sound coming from the engine, that stops on high revs. I have checked all the common causes (that I know of): loss parts and clutch, both are OK. I suspect that the problem is related to a jetting issue, maybe a lean mixture, or maybe it is related to detonation. Did someone encounter this issue? Any ideas? Your help please.
  22. So I am currently working on a 1997 CR125 and plan to make a full race build on it. But I have been noticing that there are not very many aftermarket parts the biggest being the plastics and graphics for it due to the frame,tank,sub frame, etc. I was wondering if its possible to put that engine into a CR125 frame anywhere from 98-07 and how hard that would be to do. I have a welder but I am not confident enough to weld new motor mounts. If you guys could help me out with this that would be great.
  23. Hey TT, I know there's endless topics on YZ250/ two stroke tuning in general but I have not been able to find one that helps me get my 09 YZ250 set up for my riding style and where I ride so I'm here asking for help. I got this bike around 1.5 years ago and have not known how to set it up properly. I know no one can give me a perfect set up but I'd like a good starting setup to work from and tweak to perfection. Throughout this time I've had this bike, its always been covering the bottom of the entire silencer and dripping all over the swing arm and rims with oil. Also, the joint between silencer and expansion pipe has oil around it too but I've heard I have to close the gap a little to squeeze the silencer a little tighter and stop the leakage there. I don't have too much experience messing with carbs but I've messed around with previous two strokes and tuned them a little better. I change the oil on my bike after 15-20 hours on it and clean and oil the air filter after almost every ride. The sparkplugs never last me more than a few months but recently have been lasting me no more than a few weeks. With the excess oil from the pipe and spark plug fouling you can see why I need to set my bike up to stop this. The bike: Completely stock with V-Force 3 Reeds and a FMF Shorty silencer. Usually running around 32:1 premix with 91 pump fuel because I prefer to keep it well lubricated instead of running rich. Riding: I ride enduro in Ontario, Canada. So mostly single track and some fire roads but nothing close to MX and not a lot of time wide open. Therefore, probably mostly 1/4-1/2 or 1/4-3/4 throttle range. Where I ride: Usually 0-500' above sea level. With temperatures ranging from around 15-35 degrees Celsius (55-95 Fahrenheit). If anyone can give me a setup to go from, that would be very much appreciated. Even multiple set ups for different temperature ranges or any suggestions would be much appreciated. Thanks and sorry for the long read, I just didn't want to leave anything out. Ask any questions if you have any, too.
  24. In my last post, I shared details about how the two-stroke cylinder works, in today's post I want to provide an overview of how a performance two-stroke engine's exhaust system works. Adding a performance exhaust system can be a great way to increase power and/or alter the power delivery of an engine. I would also argue that optimizing a two-stroke engine’s exhaust system is equally as important as ensuring the cylinder’s ports are correctly designed for the given application. Not all exhaust systems are designed to do the same things, and much like cylinder port design, exhaust designs are intended to alter power in specific ways. Having a basic understanding of how an exhaust system works can go a long way when it comes to selecting the right exhaust pipe for your engine. Two-stroke exhaust design is complicated and there are many different variables that must be considered when designing a pipe. I don’t intend to go into all of them, but I will share a few of the most critical. Each time the exhaust port opens to release spent combustion gases, pressure pulses are created. Modern pipe designs harness this pulse energy and use it to help scavenge and fill the cylinder. The process starts when a positive pressure pulse is created once the exhaust port opens and combustion gases leave the cylinder. The positive pulse travels down the pipe until it reaches the diffuser, at which point part of the pulse is inverted and reflected back towards the cylinder as a negative wave. This negative wave is very beneficial in pulling spent exhaust gases out of the cylinder and fresh mixture up through the transfer ports. The remaining positive pulse continues on its journey towards the end of the pipe where it encounters the reflector. The reflector acts as the name implies and forces the positive pulse back towards the exhaust port. Once reflected back, the pulse remains positive and, if the pipe is designed correctly, will reach the exhaust port just as the piston is about to close off the port on the compression stroke at the desired RPM for maximum power. Any fresh mixture which has escaped out the cylinder will be forced back in by the positive pressure pulse. The tuned length of the pipe is dictated by the exhaust port timing, RPM of max power, and the speed of sound. Pulse length and amplitude are governed by the angles of the diffuser and reflector. Generally, steeper cone angles create pulses with more amplitude but shorter duration. Shallower angles generate pulses with less amplitude but longer duration. Given these variables, it is easy to see how a pipe could be tailored for specific applications. An engine converted for road racing may utilize a pipe designed for peak power which incorporates steep diffuser and reflector cone angles so that pulse amplitude is not sacrificed. This peak power would likely come at the expense of a narrowed range of power. An engine tailored for woods riding may feature a pipe with shallower cone angles, resulting in less pulse amplitude, but a broader spread of power. The last parameter I want to touch on is how the tailpipe, which is sometimes referred to as the stinger, influences the pipe. The tailpipe creates a flow restriction in the pipe which allows the pipe to have a certain amount of back pressure. Enlarge the tailpipe and the back pressure decreases, make it smaller and the back pressure increases. As back pressure increases or decreases, so does temperature and ultimately the speed of sound. As the speed of sound changes, so does the resonance RPM of the pipe. If the tailpipe is sized too small, cylinder scavenging will be inhibited. When this happens, the cylinder, fresh mixture, and piston will all be overheated. While engineers and tuners can estimate starting pipe dimensions and tuned lengths, a great deal of trial and error testing is usually still necessary to fine tune the exhaust pipe and optimize the design. Unless you intend on building your own exhausts, this work will have already been done for you. When selecting an exhaust system, you need to focus on how the exhaust alters the power curve. Exhaust systems are tailored to deliver more bottom end performance, top-end performance, or performance throughout the power curve. Selecting which system is right for you will depend on how you want your engine to perform. If you’ve chosen to modify your cylinder ports, installing an exhaust system that compliments the porting can be very beneficial. You might be wondering about slip-on mufflers. If you’ve followed along with my explanation of how exhaust pipes work, you’ll notice I made no mention of the muffler. While the muffler can have a small effect on performance, it is not the primary factor. Upgrading a muffler is a good way to reduce weight, but there won’t be a slip-on out there which significantly increases power, in the same way, a properly designed expansion chamber can. I hope you enjoyed this write-up on key features affecting the performance of two-stroke cylinders. As for Two Stroke Handbook news, we received our first printed proof of the book this week! Needless to say, we are inching closer and closer to an official release date. To stay updated on The Two Stroke Dirt Bike Engine Building Handbook we created an email sign up for our readers. Click this link to sign up, see the new cover, the Table of Contents, and some sneak peek pages right from the book. Thanks for reading and have a great rest of your week! -Paul
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