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Found 85 results

  1. Hey, I picked up a 96' cr125 off Craigslist for pretty cheap. Learned my lesson from my last two stroke- gonna do a rebuild before I crank her up again... Anyways, pretty sure the bike has "piston slap" noise coming from the motor. I looked it up on Youtube, sounds like what it is. Is there anything special I need to know before I do a top end? I'm still a fairly inexperienced mechanic, but as far as I know, I need to get a bore-measuring tool and measure the cylinder bore before I buy a new piston. They make slightly oversized pistons for this kind of situation, right? I'll post pics sooner or later. Just gonna keep digging this thread up. Let me know your thoughts! *Edit*- The bike can roll in second gear. Noticed it when I was buying the bike. When I pop it in gear to rock it back and forth before I start it cold, it'll just roll through and you can hear the engine turn over. My guess is this is a symptom of a roached top end.
  2. My brother was rebuilding my top end for me on my 2002 yz250, and due to a failure on his torque wrench, he over tightened and snapped one of my studs . Now i only have 5 of 6 working bolts on the cylinder head. I have 2 questions. We are supposed to be leaving for a 5 day riding trip in a few days, so we don't have time to order a new one. A: can I achieve enough compression and avoid any disasters for one week without 1 of the 6? b: There is a pretty awesome machine shop by his house that may be able to make us one, but I can't locate the specs. Does anyone have the exact specs for a 2002 yz 250 cylinder head stud? Any and all help would be much appreciated.
  3. 2008 crf250r, in the process of finishing up a top end rebuild, and after installing the timing chain onto the cam I deciding to hand crank the engine slowly with the kickstart to see if everything was alright. There is a distinct knock that sounds like it is coming from somewhere in the cylinder each time I turn the engine over. What would be causing this sound?
  4. Hi All, I am going to be rebuilding the top end of my '07 DRZ 125L. I am what most would call a complete novice when it comes to rebuilding engines and am just looking for general information on parts required and any other things that I could need or would be helpful. I am also considering putting a bbk 150cc on it when I do the rebuild, Any thoughts? Thanks.
  5. So I have a 1998 Yamaha Yz80, and I need a new top end. I found a 2002-2017 Yz85 piston kit, for a very reasonable price, and I was wondering if it would be able to fit my 98 Yz80? Would the piston, wrist pin, bearings, rings, Etc be able to fit? And will it work?
  6. A 1994 KX125... This is my first 2-stroke (and a new purchase for me), i was told by the previous owner that the oil from the exhaust was a sign that it needed a new piston ring. Replaced the piston and ring and now the bike bogs down bad from a stop/very low speed while in first gear. New piston and ring (Wiseco spec sized for the year but is flat while the original one was crowned) Cleaned the carb (42 pilot jet with a 158 main jet) 800' above sea level Reeds look great Repacked the FMF silencer (still have oil out the exhaust so I know its running rich) I just can't figure out what else to do or check. The bike has great pull and power in the upper RPM range of first and all through the rest of the gears it pulls strong. Just looking for something that I might be missing. I have been searching this forum along with others for an answer to the issue I am having but have been unlucking in finding any leads...
  7. I recently purchased a 2010 KX250F from a friend of mine that had been sitting in his garage for about 5 years. The bike seemed to be in decent shape and the price was right so i picked it up. I went through most of the bike before riding it (air filter, oil, greased all the bearings, adjusted suspension, changed all the fluids, etc) The valves sounded a bit loose so i decided to have a "Buddy of mine" adjust the valves. I get the bike back, go for a ride and the cam chain tensioner falls out while i was riding, luckily i caught it very soon after it happened and it never jumped timing. I put the tensioner back in and continue to ride the rest of the day. as the day goes on the valves sound much looser than they were originally before the adjustment was done, I decided to call it a day and tear the bike down myself. I shim the loose valves and button the bike back up, but now the thing sounds god awful. Straight up clacking coming from the right side of the top end. Since then ive probably had the bike apart and back together 4 or 5 times trying to figure out the problem. Its not the auto decompression valve, every valve is in spec, timing is solid, and the cam chain tensioner is working fine. I'm stumped. anyone have any thoughts?
  8. I just rebuilt my kids 2013 YZ-125 that I had the cylinder professionally oversized by 2mm from Millenium Technologies last year. It made it a 134cc. I just rebuilt the motor for this season, I had MT-LLC re-plate the cylinder and match it to a new piston. I also had them deck the head for race gas only. My sqush is at .038. I plan on running race gas (sunoco 110 non oxygenated) at 32:1 with Redline (which is what I ran all last year). Here is where my concern begins. I did a compression test and it is right at 220psi. Will I be eating main bearings quickly? Will this motor hold up for a season with exceptional maintenance? Should I advance my timing about .002 to compensate for the high compression and reduce the pressure on the rod? I was told to simply double the base gasket and it will work. IF I do that, What will that do with the timing and jetting? Just a little out of my league with this much psi..... Please help with ideas. Thanks.
  9. I have a bike someone gave me thats in pieces and I have a good 426 bottom end and a good 03 450 top end. Can I put these together and what if anything would I have to change?
  10. I just bought a 1999 kx 125 and wanted to inspect the top end so i took off the pipe and looked through the exhaust port and saw the images below, I am new to this but i think that that is blow by meaning i could use a new top end. What do you guys think that I should do, if anything?
  11. I just put an fmf powerbomb on my 2006 yz250f and started it up a few times and have began to hear a slight tick in the top end. I also turned the bike over maybe 20 times without starting it to test for air leaks in the exhaust. Could this have caused too much back pressure and thrown off my valves? (the muffler plug WAS in). I know the normal 4 stroke engine noise, but this doesn't sound too normal. Could you guys take a listen and let me know? Hoping it's a normal sound. Any help appreciated! Video of sound:
  12. This is my first top end rebuild. I just got the head off, cylinder and piston removed. There's definitely some wear on one side of the piston and cylinder. I'm replacing the piston, rings and head with a VHM. Should I be concerned about the wear in the cylinder? If so, would scotch bright suffice? Also, I gave the bike a good cleaning prior, but as more and more parts came off, it was apparent that things were still a little dirty. Can I clean the cylinder prior to putting it all back together. Lastly, the cylinder bolts were pretty corroded; well at least 3 out of the 4 were. Should I wire brush these? It'll be hard to keep junk from falling into the bottom end... The bike is a 2006 RM250 Thanks
  13. okay, so I recently rebuilt the top end of my 2007 yz250f as it went out on a ride. Anyways during the winter it was taken out of the garage and and started for about 2 minutes before it "seized" At least that's what I thought until I took it apart. The kick starter was stuck and wouldn't move and after I took the top end off I saw that the crank was stuck and I was able to get it moving again. So the cylinder was still in good condition and has no big scratches, and now the crank is moving freely as it wasn't before. Is this a simple top end job and I must've not put it back together correctly or is it something deeper involved? Thank you, any input would be appreciated.
  14. Hi guys, I’ve got a 2005 kxf250 here and Im concerned about how oil is fed from the bottom end to the top end ... anyway I bought it blown up... I’ve had to buy new bottom end casings, new cylinder head new valves all that lot.. but once it was put back together and oil was put in, I went to re time the bike and noticed there was no oil by the magneto hole, I took the side cover off to inspect whether oil was actually in this side casing where the conrod and big end bearings sit and there’s nothing? But normally oil is fed through the timing chain to the top end isn’t it? you can clearly see by the sight glass there is the right amount of oil inside there (not to mention I measured the amount of oil I put in anyway) I’m just wondering if there’s another oil top up point I’m struggling to find or is this just how the bike is? Because there is two oil drain hole plugs so it’s just a thought, any advice will be appreciated!!
  15. Hi I just done a top end rebuild and a few other bits too my bike change the clutch cable,got it started sounded like a ticking sound coming from the engine after listen for a minute I think it’s coming from around the clutch area and it starts to tick faster if I rev it ? I disconnected the clutch cable and still was ticking. Even if I push it with the bike off I can here it . The bike won’t go into gear at all now it feels as if it’s half in gear and then clicks out any body able to help me ? New here thanks 😃👍
  16. So just a short background I was heavily invovled in the ECEA and raced since I was 6. At 16 my 2006 crf250r blew up and than I broke my leg. Long story short I'm now 26 and just purchased a 2000 RM 125 and I need some help. It has a rebuild bottom end but the top end needs some love and there are small parts missing from the bottom end as well. Both cases are together trans is all there and mostly everything is done. The main issues I'm having are locating parts and making sure I get everything that's missing like washers and spacers where needed. I just need a few knowledgeable people to help me put this bike back together. I can give pictures and as much information as you need to help. As soon as someone replies I think it'd be easier for me to just take pictures of everything I have and you tell me what I'm missing. Also if anyone is selling parts and close to south jersey I'd be more than willing to purchase parts.
  17. I have this spark plug o ring left to install, and I cannot for the life of me figure out where to put it and I don't want to chance it and install it the wrong way. will someone please tell me where this thing goes.
  18. Alright, so I just got done rebuilding the top end on my 07 KX 450F and as I am getting ready to install the top of the cylinder head I notice I have one last piece remaining that I can't account for. I mark everything and take several pictures so I can make sure everything is put back together perfectly, but somehow this piece evaded me. I showed where I think it goes in one of the pictures I provided. Can someone tell me if I am right or if this piece goes somewhere completely different?
  19. hi, my 06 yz450f was perfect, it would start first kick when cold and hot, with putting a good amount of hours on it started getting harder to start when cold, now it wont start at all when cold unless pop started, doesn't idle and runs choppy until warmed up once warmed up starts first couple kicks and has power. my guess is the valves need to be shimmed? I was going to have my local shop check the valves then I was going to put a new top end in after anyways I put this top end in 150hrs ago. (bike was taken apart I used the piston that came with bike) im going to have to do better with keeping up with valve maintence this time around.
  20. 2008 crf250r. Just installed new gaskets for top end and new rings. I also adjusted the valves since the exhaust side had tightened up. I cleaned the jets in the carb prior to the top end work (which took about 3 weeks) It is still as difficult to start as before and i have to give the throttle a slight twist when i crank for it to start up. It will not idle and feels like it's significantly slower. I didn't ride it much before the top end work so maybe I'm just used to my 450 but it seems like it's sluggish. It doesn't pop at all though so what could be causing this?
  21. I've got a 93' xr650l with about 7,000 miles total. 1,000 miles on top end rebuild by dans cycles in round rock tx. I bought the bike about a month ago and noticed a weird noise in the top end. It wasn't happening often until recently. And it only occurs during a specific low end rpm. A local mechanic diagnosed it as potentially a "spark knock" given that he saw a worn ignition coil,spark plug boot. I replaced those and it still made the noise. I run supreme gas only, adjusted the valves to spec twice just to make sure and it still makes the noise. When adjusting the valves, i manually rotated the engine and i believe i have narrowed the sound down to the right side exhaust valve. It seems to catch for a second and then release suddenly, making the noise. Could it be a loose valve seat? Decompression mechanism in the cam? help haha youtube video coming soon
  22. 2015 CRF 450R. 70~ hours did a top end and now it wont idle. After installing the top end and riding bike it wont idle once hot. I can set the idle cold to about where i want it but once i give it gas and its warm it either idles at 3k rpm or dies. WHen i say dies as soon as the throttle is not open the bike goes->0. Even when its cold and you give it throttle it almost hangs at 3k then settles to 2k but once fully warmed it dies. I have cleaned everything in addition to the steps below. Any suggestions would be greatly appreciated as im without a bike and losing hair over this. It seems electrical as i didnt notice that much of a power loss I have tried: remapped it all sorts of different ways, swapped throttle body from buddys bike that runs(TPS, injector, idle sensor, idle adjuster), checked all sensor and cleaned them, put buddys fuel tank on ( filter, pump etc), gas is not old, checked timing chain alignment( although the factory lines on the cam shaft are not perfect i believe with 98% certainty the cam is aligned properly) , air filters clean, no tlow on anti freeze, IAC sensor changed, sorry if this is in the wrong section, just trying to get some help
  23. Wondering if I can reuse the head bolts for this bike or if I have to get new ones every time i rebuild the top end? its a 2008 CRF250R
  24. So, I have a 1998 Yamaha yz80, and it's had a lot of hours on the top end, so it's time for a rebuild. I have a neighbor who is going to help me with it, so i havent taken it apart yet. I'm trying to figure if my bike needs a whole new piston kit, or a gasket kit, or does it need new reeds? So its lost compression. Way less then what it used to be before. The bike is really hard to start, and it fouls my plugs like none other. It doesen't have too much of a power loss, although, the powerband has become weaker. I just want my bike to be running like how it used to be, and I don't want to spend a lot of money on it. It will start sometimes, but most of the time, it will only bumpstart. I appreciate you viewing this, now, so let me know of what I need.
  25. Hey everybody! I own a 2005 crf250x that has never had a top end rebuild, Or any rebuild of that matter. I plan on getting the top end rebuilt this winter so that I have no time crunch to get it done, and I can go into next riding season with it! So anyway, let me get into what I need help with: I want to rebuild the engine myself, but no one in my family has any clue how to work on an engine. We have always been ride/drive, change the oil every few months, and ride some more. Now that I own my bike I want to keep it right. So with a 4stroke, is it reasonable for a guy with no experience or past knowledge on engines to rebuild a top end? I have watched a few videos of rebuilds, and it doesn't seem too bad, but there does seem to be a few things that seem to require some real knowledge. I would love to save the few hundred bucks by doing it myself, but I am afraid that I will missing something (ex: not replacing the piston even though it should be). Also, if I am to do this myself, what tools would I need? How risky is this build to do by yourself. I may be able to get my cousin (who I ride with) or my dad (who is rather mechanically inclined just not experienced with engines) to help me if it seems needed. Overall from the rant: I would like to do it myself, but I am fully intimidated. Is it worth the risk for the money saved and knowledge/experience gained? What tools do I need (100% list)? Would I need a helper/partner to do this? Thank you in advance! I hope you are willing to have more of a conversation about this!
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