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Found 53 results

  1. My kx100 won't start. It gives a little purr when I kick it like it wants to. Spark plug is good. I never took apart the bottom end so idk if that could be bad. But I changed the piston but don't ask why but I used an old ring on the piston and one new one. The cylinder has a gash in it kind of like it was grinded by the piston a bit but that may be a problem. It's an 08. I tested the compression and got 85, and then tested 75 so it's bad. Could one bad piston be the problem? The piston was torn up bad so I'm sure the ring was bad. It was sharp too. Could that solve it? Thanks
  2. I have a 2006 kx250f starts first kick when cold takes a few kicks when hot but i was out riding with my buddies and i let one of them ride my bike when he went to start it up he kicked it over and was telling me it has very low compression and that it should not be that low, is this normal or a problem im just looking for someone who knows what there talking abouts advice cause if its a problem i wanna fix it to give you an idea how much compression there is you can push down the kick starter with your hand but it still takes effort. pic for attention
  3. This has been an ongoing issue, as I am sure some of you are beginning to notice.. sorry for the somewhat repetitive posts in advance. My valves were out of spec, I was only getting 85-90 PSI of compression. I shimmed my valves to the correct clearance, and I got the compression up to 150 psi. Now after riding my bike for 15-20 minutes, it will start doing the same thing it did before - it will idle super low and eventually bog out. I had the idle adjustment turned up very high, when I gave it a little throttle the idle would kick up for a couple seconds, then it would settle back down to extremely low and bog out. To me this sounds like something with the idle air circ, or jetting. Could something with the valves cause this as well? Want to get a second opinion before I send the head in for the $500 rebuild and still have the same issue. Thank you all again!
  4. My 2016 wr250f already run 8000km (5000miles). If it climb a steep slope with low rpm, I will heard some knocking noise from the engine, I guess came from the valve. If I keep throttle few seconds, the engine will stall and cannot start. At this monent, the kick starter is easy to push with a single hand. So, I guess the valves are jammed. But few minutes later, it will become normal. This happenned twice in the last 3 rides. Any idea about this symptom?
  5. '09 DRZ400SM I replaced the rings and head gasket, and she starts up and runs just fine. Checked the compression after it was warmed up (air filter removed, throttle pinned open) and got a reading of 90psi. Put a teaspoon of oil in the cylinder, compression barely went up to 95psi. I'm at altitude, so the stock 135psi as per the manual would be 115psi here (5280ft = 15% compression loss). So right now I'm at a loss of 20% compared to a new bike at this altitude. is 90-95psi acceptable at this altitude? I'm not sure what normal compression would be for a 11 year old bike with new rings. I know a leakdown test would be best but I don't own one and don't have the funds to buy one right now. Otherwise I would just pressurize it and listen for leaks.
  6. 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.
  7. 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.
  8. Hello fellow ThumperTalkers. I recently bought a 2020 YZ250 and have some questions on the suspension. Here is some back story: - I am 130lbs w/o gear - Mid-pack B class rider (still new to the 250 2-stroke so I am trying to get to the top of B class) - I had a 2016 YZ125 and left the springs, sag, compression, and rebound completely stock. The bike handled perfect, but I never adjusted the suspension so I don’t know if it could have been better Now with the YZ250. As I said, I am 130lbs w/o gear. Would I be able to get away with using the stock springs? If you’re around my weight and own a 2006+ YZ250 with stock springs, what is your setup (compression, rebound, etc.)? BTW, I will be raising my forks up 7mm in the triple clamps. Any help would be greatly appreciated!
  9. I bought a drz400 in pieces but the motor was assembled just put the wiring harness and all those goodies back on. Timed it to Front exhaust cam to 2 and the rear intake to 3. 15 pins in between and to TDC. I went to fire the bike its got a new jug, new rings, new piston. It will pop and shoot flames when it has compression but sometimes it’ll just spin freely with no compression sounds. if i keep winding on the starter it gains and looses compression over a certain amount of time. For 10 seconds winding the starter it’ll have compression, the next 10 seconds it wont have compression while winding the starter. Its very weird ive never seen anything like it. I hate to take it to a shop, i do everything myself. Thanks.
  10. In the manual, it appears that the rebound is on the same side as the preload adjuster and the compression in on the side with the radiator fill port. Yet, on the forks, there is an engraved R on the left side ( same side as the radiator fill port) and a C/P on the side of the preload adjuster. As I read/look at the manual, its is backwards based on the engraved markings. So, what side adjusts what?
  11. First bike new to all this 04 kx250 checked valves today huge gap between cam and buckets zero compression plan on ordering shims hopefully this will fix my problem? Anything else to look at piston looked pretty good from what I could see. Thanks.
  12. Hi Guys, I have an 02' CR125r. I recently rebuilt the top end (new piston / rings / gaskets) and checked the tolerance of the cylinder to confirm correct piston size. Bike started and ran great right after the rebuild. The next week I went trail riding and initially the bike ran like a top! After about 1-2 hours of seat time, (not riding balls to the walls) the bike just died mid ride.. I let the bike cool down and then found I had zero compression. I replaced the plug as a quick troubleshoot but that did no justice. I have yet to tear the top end apart. Any thoughts as to whats going on? Or has someone else experienced something similar ? Appreciate the help!
  13. so me and my buddy just bought a 06 rmz450 that supposedly needed a valve shim job. it ran when we got it but the guy had to pull start it with his truck. later after removing the valve cover we discovered that someone had already attempted to shim valves and in doing so broken off 1 of the exhaust cam journal bolts and stripped out 2 intake cam journal bolt. I currently have the intake tolerances at 0.005 in and the exhaust at 0.008. the motor to my knowledge is timed properly. I have the dots facing outwards level with the block and the dots on either cam facing upwards while the motor is at tdc on the flywheel indicator. I reassembled the bike and now it has no compression. the little plastic threads on the decompression cable are stripped and I don’t know where it’s supposed to thread into. could this be the cause of no compression? it’s just hanging on top of the block. i’m planning on selling it after i do the work. thanks
  14. I bought a "2000" yz125 from someone. Shortly after purchasing the bike, I checked the vin and realized it is actually a 1999. Off to a good start. The previous owner told me he put a new top end in the bike and saw the clearance value of 0.002 inches on the wiseco piston box, so he thought that meant to bore the cylinder out the much... no big deal, its a pretty insignificant amount. I start the bike up and ride it around, but it has practically no power at all. It revs up fine on the stand, but it has absolutely no power when riding. So I started checking stuff. The power valve actuator arm moves when the revs go up, good. The valves themselves are new (he also replaced the entire assembly). The valves do no stick, and they move with the actuator, so I know that is working properly. Next I check the reeds, they are not damaged at all. Then I check the exhaust. It does not appear to be blocked anywhere, so thats out of the question. Then I do a compression test, and it comes out to 105 psi... found my problem. I'm just not sure why it has no compression with a new top end. The clearances between the cylinder and the piston look good, and the ring does not appear to be damaged (I have not take the jug off the bike yet). The cylinder walls looks bad though. There is no visible crosshatching, and there are weird patterns in the walls. The previous owner took the cylinder to a friend of his to remove that 0.002 inches, so I'm assuming he did not hone the cylinder properly. I'm kind of at a loss, and I don't want to replace the whole top end again. I am attaching pictures of the cylinder and a view of the piston and exhaust valves from the exhaust port. Does any of this look right? Also, he said that he lost the "top cap" when doing the top end. I assume that means the head because the motor mounts don't line up properly. He said he took a "top cap" from an rm125 or something that was laying around the shop, so I'm thinking that could be a possible culprit for the low compression. Any insight is helpful. Thanks.
  15. Just got my ssr today will it be easier to start as i break it in. today it turned over after 1 kick sometimes and 10 kicks other is it the carb i bought a vm 26 but was waiting for the bike to break in befor installation
  16. Hi guys! I'm wondering if any of you know for sure if the advertised compression ratio of CP Carrillo piston for our bike is achieved with the single layer base gasket (.010" thickness) or with the standard 3 layers base gasket (.030" thickness). I'm asking this because I noticed they offer the same piston (12.5 cr) for both LTZ and DRZ but with different gasket kit, and it seems odd to me since it's the same engine.
  17. I’m new here. im doing a build on my 86 cr250 and I was wanting to shave the head for more compression. I was thinking, would it work just to put the head on the cylinder without the gasket and keep shaving it till it touches the piston, and then put the gasket on? What are your thoughts?
  18. Hey Guys, I finally updated my old 2012 rmz with a run out new 17. I managed 430 ish hours on the old girl with 3 rebuilds no real dramas. Problem is the new 17 is already giving me the shits that something is not right with it. The very first time I started it it smoked alot, I mean alot. Its my 5th brand new rmz and none have smoked like this. Then with the first oil change post run in there was alot of mater on both the oil filter and screen. Second oil change was after a xc race and trail ride both in the same weekend, 5 hours. That oil smelt like petrol. and it seemed noisy. Then this weekend I went to do the acerbis 4 hour, was going good too 3 hours in and the thing got real noisy I had to pull out sounds like its going to blow up. Thing is it goes like a cut cat. Anyone had issues from new?
  19. I have a drz400s with a +4mm stroker kit. I was running a 4 layer base gasket to lower the compression bit ended up blowing a head gasket anyway from not tightening down the head enough ( did the 34.5 from the factory manual saw on here it was supposed to be 43). Now when the head gasket blew the head warped slightly so I got it resurfaced. When I got it resurfaced the machinest said he had to take .07 inches off which seems like a lot to me. Now with a stroker and that reduction in clearance I'm worried about where the compression ratio is. Has anyone in a similar situation got any insight? Should I be alright with a 4 layer base gasket or am I sitting on a ticking time bomb. Thanks.
  20. Hey guys, I bought a 1998 yz250 that needed a top end rebuild. When checking the bike out the top end was already off, piston still on the rod. It turns over freely. I pressed the kick lever down and the piston obviously goes up and down. Basically the bike was a $700 buy that needed a top end. no big deal. new excel rims and dunlop tires, had everything to rebuild the top end already, new renthal bars, grips, etc. plastics worn out but no big deal. well worth the $700 in my book. So here's where my problem lies, after putting the top end back together, i'm finding it super difficult to kick. before i put the head cap on, the piston moved up and down smoothly in the cylinder as i pushed down on the kick lever. as soon as i put the cap on and the spark plug in, it became almost impossible to kick. I stand on my dirt bike stand to give me leverage on the kick lever and put all 200lbs of myself on to the kicker and i've gotta give it a little bounce to get it to kick. When it does drop all i hear is the piston stop at the top of the cylinder like its got all the air compressed. I'll reset the kicker and drop down on it and it'll kinda drop or get hung up like the piston doesn't want to suck back down and when the piston finally gets low enough in the cylinder i can hear a thump of air out the carb. I tried kicking this thing for a half hour with the piston getting hung up because of the compression not wanting to let it go. At least thats what i think is going on. and when i get the piston to clear the intake, it finally releases the trapped air. As far as spark goes, i've got a ngk 8es or something like that. not sure off hand. I do know its not the R plug. spark was there, wasn't the strongest spark but not the weakest either. Any idea on what could be going on? I think my next step is to take the plug out and see how easy it'll kick with out the plug in it. Any ideas would be appreciated, thanks.
  21. Should you still have to use the decompression lever on the compression stroke if no spark plug is in the bike or should it turn very easy?
  22. Hello All, I bought a 1995 Honda XR 250L cheap from a guy down the street who was moving. The bike ran but not well. When I received the bike it did not run. I do not know a ton about these bikes or dirt bikes in general. I do how ever notice a couple of things on the bike. The carb was dirty and I attempted to clean it. I didn’t notice that the diaphragm thing inside the carb. was rusty and didn’t look to good. I do not however know what it does or if it should be replaced. I then notice that one of the throttle cables was missing. If you are looking at the handle bars it is the lower cable. I went to buy a replacement but I am unsure of whether it is cable A or b. Lastly I noticed that the decompression cable is broken off and missing from the bike. I would like to see if this bike is worth putting the money into. What should the compression be? How do I initially set up the carburetor? Will it start without the decompression cable or other throttle cable? Does anyone have a pdf of the manual or a YouTube channel to help? Thank you for the help guys!
  23. My husqvarna tc 250 2011 start to loosing compression ..Yesterday i tried to start it 20 light kicks nothing .Later i came back tried 4 hard kicks to low compression and started normally.Bike runs fine its not smoking , no power loss nothing.Bike have around 50 moto hours after top end .Sometimes it have really big compression and after two kicks almost none.Maybe decompressor is stuck open or something i have no clue...Thanks for any advice
  24. I have a chinese WildFire dirt bike 250 pro and i got the thing on new years day 2018 for $300 it ran but it wasnt healthy its a four stroke and just recently completely cleaned the carb and it runs but i have to physically pour gas down the cylinder to start it.. Its got electric start but it doesnt spark and only sparks when the bike is warmed up so the only way to start it is pour gas down the carb and kick it or use starter fluid in which i dont have nor do i want to use it.. I just need help right now i have a scheduled trail ride with my buddies in a few weeks so i really need this thing to start without pouring gas down the cylinder (i dont pour much at all) UPDATE: the intake tube from the carb to the engine was not screwed in all the way so i tightened the &%$#@! out of it and i kicked it and it started after 4 kicks (not too cold but its 35 degrees Fahrenheit out right now) thanks guys for the suggestions!!
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