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Found 19 results

  1. Hi i have a 2008 kx250f with low compression it has a compete new top end including a new cylnder head with new valves and every thing there is no leak in the intake and egsoust valve also i did test with cams conected and not conected or with full throtle i tried every little thing also i bought the bike not running with low compresssion when bought it had no compresstion and with a new piston it had 65 psi and then i realized all valve seats are meesed up and valves so i bought a brand new head with all new valves and gaskets and all but still 65 psi and before the head was leaking and it is not leaking now. i work on bikes so i know about the timming chain and stuff all those stuff have been cheaked when i spray starter fluid fire comes out of the intake with no pop or any sound just fire out of the intake (with timming and in spec valves) plese help me i have spent alot of money and dont know what to do also i live in ny and will pay some one to help me thank you
  2. Hi guys: Finally finished my RM85 top end, but after 3 heat cycles I´m getting no more than 100-110 PSI of compression, and after some time of operation, seems like one of the head bolts were leaking coolant, at the same time that there was a lot of overflow coolant. Teared down yesterday and found that my cylinder head was pretty irregular, aswell as my jug (here´s the deal: the jug has grooves, but I was delievered like that from the shop, I don´t know if that´s normal, I can feel them with my nail easly) , and seems like one of the orings don´t fit perfectly to the space. What could it be? Fouled a plug tho, scared the hell of myself, thought that she blew up. I was thinking about sanding the head, putting some silicone in the orings, and check the compression
  3. 2013 kx250f just installed new valves new piston and have 60 psi compression. I’m baffled. Valve clearance are good no warped head cylinder not worn. Any udeas
  4. Recently put a new piston and ring in my 125, expected it to dramatically increase the low compression I was experiencing before. Cylinder looked free of damage to me and could still see old hone marks from last time. Can easily run the kickstart arm with a weak hand. Can usually get it to run after some tinkering but bogs in the mid where it should snap into power. Used to love this bike now it’s giving me gray hairs. Any advice appreciated
  5. (Just to clarify I have never owned a 2 stroke so I don't really know what I am doing but I am pretty mechanical so putting stuff together and rebuilding stuff if pretty easy but NORMALY on a 4 stroke) Hello, So I recently purchased an 04 ktm 65sx as a pit bike for myself and there seems to be an issue with it somewhat bogging up hills I say somewhat because it doesn't feel or sound like normal bogging. So basically what happens is it feels like it is pulling me fine up the hills at first then the "braaap" sound that the 2 strokes make will go away and come back over and over again. when the sound is off there is basically no power I am just kind of rolling is what it feels like then the sound will come back and I will feel the power that it is supposed to have. Also when I am driving it on flat land it kind of does the same thing it is just in a smaller fashion. So I am thinking it might be something to do with the compression which is less than adequate (I don't have a compression tester I'm just guessing from the feeling of the kick). So it would be really helpful if someone that knows about this could point me in the direction of what I should do, maybe get new piston rings or new piston entirely or new head??? Also when I got it and checked/ replaced the oil it was very milky so I have a new water pump seal coming in. I NEED HELP and this is above my 2 stroke knowledge any help would be nice and if someone wants a video or a picture of something specific please tell me!!!!
  6. I have 1992 kx 125 it has low compression bike was running ....so I decided to try and solve the problem so took the bike apart took the head off the cylinder ... The cylinder wasn't that bad then checked my crank my conn rod had a little then usually play so now I got a new pro x piston standard bore and rings new top end gasket kit and spark plug no I didn't do a compression test ect... now I got the bike back together got more compression then I had but after a kick or 2 no compression then comes back I kno it's a old bike..........do u think it's time for the cylinder to be re sleeved and crankshaft rebuild need help will this solve my problem ????????
  7. Hi All, I have been looking at a 02 yzf426 for my mate. as you all probably know they have a compression lever that you have to pull when starting otherwise you can’t kick through the stroke. He was riding in the weekend bike running mint then died, now has lowish compression, you can now kick through the stroke. Wasn’t smoking or hard to start prior to the issue. the only thing I noticed was the right front cylinder bolt was loose and looked to be leaking oil from the base of the cylinder. i have torn engine down, piston and cylinder look great. anyone have any ideas whether valves may cause the sudden issue or why the oil is leaking from base gasket and if this could be the issue. thanks in advance for the help. Chris
  8. My son has 1982 XR100, it's always burned oil (mostly by blowing it into the exhaust pipe and smoking like crazy). I knew eventually we would need a rebuild. About a month ago, his friends and he were riding it non-stop without checking the oil and burned up a piston. The rod was fine, just the piston cracked, scored the cylinder wall badly, and broke the wrist pin. So we decided to the BBR 120cc big bore. I did everything by the book (pdf xr service manual). The kit comes with new valves, springs, lifters, valve cam, rings, piston, and cylinder, and gaskets. The cylinder comes pre-honed I assumed since it was nicely cross-hatched. I lapped the valves, got the rings in right-side-up, made sure their gaps are 120 degrees offset, and checked the valve clearance. I set the timing as stated in the manual. My ring gaps seemed fine from what I could tell. Oh yeah and put plenty of oil in the valve pocket thing for initial start-up. Before attaching the wrist pin, I poured some oil in the cylinder with the piston down some just to make sure I had no leaks. Seemed fine. When I first went to kick it I could tell the compression was lower than before. I thought well maybe it's supposed to be that way -- it's a bigger bore, right? It does start after 1-2 kicks almost always. I let my son take it for ride and he said, "I dunno, dad. It seems worse than before." I took it for a quick ride and it WAS/IS worse than before the rebuild. I checked the compression and it was in the 120psi range. From what I understand it should be much higher. I'm at a loss to what I did wrong. But it must be something. Note: I have not up-jetted yet. And I haven't checked the valve clearance again after riding it a bit. My next step is doing a leak-down. I did notice some oil bubbling around the spark plug and burning off -- it's a very small amount. The spark thread is in tight and threads seem fine. Can anybody out there steer me in the right direction? Thanks all 🙂
  9. Hi guys I recently bought a 2004 Yz250 which was supposedly rebuilt a couple hours after riding it started rattling and on return to my truck I realized it had lost all the compression I can now crank it over by hand with no resistance and a new metallic rattling sound coming from somewhere it sounds like maybe the bottom end. I’m pretty lost as to what I am to I took the exhaust off to look at the piston and from what I can tell it looks like it’s in pretty rough shape the cylinder walls don’t seem to have any obvious gouges however I am yet to pull the cylinder. Any advice or possible hints would be great I’ll update more as I go about it but for now my only plan is to pull the cylinder and check from there. I am concerned that the piston seemingly has only one ring and not 2 like Normal and am wondering if maybe that could be part of if not the issue??
  10. Hi! I've purchased a YZ125K 1983 with low compression. I have not removed the cylinder yet and inspected the bore. But my question is if it is a nikasil bore on those old yz125 or is it cast iron cylinders? I'm hoping that the bore is ok but if not it would be nice if it's a cast iron cylinder and just need to rebore and get an oversized piston. Sincerely FutureWorld
  11. I got a 1990 cr125 a while ago and the cylinder and piston were in pretty bad condition, so I sent it to millennium technologies and had them do a 144 bore on it. Of course this also came with a new piston and ring. After assembling it the first time, it wouldn't start at all. I took it back apart, measured ring gap, resurfaced the head and checked it with a straight edge, etc... Everything checked out. I put it back together and it actually starts and runs now, but not very good. It starts easy enough but it has almost no low end power and refuses to rev out. After measuring the compression again, it's getting about 110-115 psi. What else could be causing the low compression? Is it possible I bent the ring when installing it?
  12. Hey, I've been fixing a 1992 kx125. When I bought the bike it had little to no compression. My compression tester barely read anything; I could turn the kickstart over with two fingers. I took apart the top end: the cylinder and piston were in good shape, no scoring on either, but the ring was shot. I replaced the ring and gaskets and put it back together, I made sure the ring was the correctly installed: correct side facing up, gap around the nipple. The compression is better, but I can still turn the kickstart over by hand, but I do have a little more resistance. Still, the compression is only 50psi. I didn't see any leaks from the cylinder or head. Any ideas why I still have low compression?
  13. I bought a 2004 DRZ125 for my son last month, it was an upgrade for his Honda XR80R. We live in a rural area and he rides his dirt bike daily. Last week he called me to tell me his bike would not start and it had no compression. He's 11, he said he could push the kickstart with his hand. I have only ridden the bike a couple times, the last time it died on me a few times when I came to a stop (stop sign) after going wide open for a couple minutes. I found it difficult to start but as long as he could start it, it was good enough to make him happy. I stopped at Harbor Freight and picked up a compression guage to try and figure out the problem, it read between 85 and 90 psi (I tried a few times to make sure I was getting a consistent reading). I figured maybe a ring broke but not sure... I have some knowledge of engines but definately no expert! Deciced to take the head and cylinder off to inspect. There was a lot of carbon on the piston and some on the head/valves but nothing I found was way above average. The rings are all good and the cylinder looks very good. I cleaned all that carbon off and put it back together and adjusted the valves. (I was at top dead center but not sure if I was on the compression stroke) I did another compression test and now I barely got 35psi. Called a mechanic friend who told me to take the adjustment screws on the valves all the way out and test compression again. After doing that I got 90psi, same as before I took the top of the motor off. Now... Unsure on where to proceed, I think maybe the rings are worn (It seemed prettry easy to put them back in the cylinder) or the valves are not seating properly? One more thing, as I was taking the head off my son looked in the oil sight glass, there was nothing in there. There is oil in the engine but not enough to show in that little window. When I picked up the bike last month it had a fresh oil change and it read perfect in the little window. The bike did not smoke when it was running. I was told by the seller it sat for over a year in his garage, he cleaned the carb and put it up for sale Any pointers on what to look for and what to replace would be very appreciated
  14. Heres a strange problem for the community, I have a bike thats failing a compression test but passes a leak down with flying colors... 2012 KTM 250 SX-F Valves spot on, clearances spot on New cam chain Dirt Tricks cam chain tensioner HAS fuel HAS spark 4% leakdown on the leakdown test FAILS compression test horribly Thoughts?? I am flat out stumped...
  15. So I got an xl185 (4 stroke Honda) which I bought in the summer. Bike had a very poor electrical job and the wrong cdi. It used to start up first to third kick. Now it doesn't. I was playing around on it today for a good hour trying to get it started and once I did, It osunded like there was a rattling/clanking in the engine head. My mechanic said that the bike had low compression and needed the new CDI (As I took it to him when is wasn't running). I read an article by a guy called the motorcycle mechanic saying that it could be one of 3 things and I could test it with oil in the chamber, and seeing if the compression changes. Is the sound caused by low compression? Would it be okay to leave it if I am selling the bike? Also It is harder to kick when gas and choke is on rather than when it is not. UPDATE: Bike sounded fine a few months ago and kicked about the same (Had some resistance)
  16. SOLVED*** No timing issue, just had trouble lining up TDC 🤦 Going to rebuild top end to fix low compression. Thanks for the help TT So I bought my 2003 crf230f a few months ago from a friend. The bike has definitely been ridden, and was blowing a little bit of smoke when I bought it so I knew the rings would be toast sooner or later. After a basic tune-up the bike ran really strong and I continued to ride it a few times a week for a couple months with no problems... Until last week when I was riding and it died on me. At the moment when the bike died, I was coasting down a hill so there was no extra stress on the engine, I just noticed the engine shut off- almost like running out of gas. From that moment on, the bike would not start so I towed it home and checked the essentials... Air, Fuel, Spark, Compression. Air- The new air filter I installed when I bought the bike was already covered in dust, so its possible the piston rings got even more dusted. I cleaned and oiled the filter anyway (the bike wouldn't start with the filter removed). Fuel- I recently changed my jetting to Mike Coe specs, and installed a larger pilot jet to eliminate popping on deceleration. The bike ran great with the new jetting and I know the carb is clean. I went ahead and cleaned out the gas tank and fuel lines and cleaned out the carb yet again. Spark- Spark plug was white due to running lean before I changed the jetting. Plug turned more of a brown color after jetting, indicating better A/F ratio. Replaced spark plug anyway and can see strong blue spark. Also, gas is making it to the plug. Finally did a compression test and had low compression. I adjusted the valves which were a bit out of spec, and saw no improvement. A wet compression test (one tsp oil in plug hole) showed higher compression, but still low, indicating the piston rings are toast. I ordered new rings and top end gaskets and will rebuild the top end next week. I was also wondering if I have a timing issue, since the engine at TDC (pic 1) shows the cam sprocket about 30 degrees (in the retarded position?) off from being horizontal with the head, as it should be according to the FSM and Clymer manuals. Also, when cranking the engine CCW by hand, the flywheel tends to spin past TDC and happens to align the cam sprocket perfectly horizontal with the head. Is my timing way off? Also, the flywheel has a || mark (pic 2) near TDC that I used to adjust the valves. Just today when I took the pictures, I noticed a |F mark (pic 4) that usually spins past quickly so I never saw it before. both marks appear close to TDC but the engine always wants to spin to the natural position (pic 5). Where is my true TDC? Manuals only show a |T mark. Are the cam sprocket lines supposed to be horizontal with the head? Maybe it jumped a tooth? I have read the cam chain tensioners are known to fail also. Edit: Found the T mark, updated photo near bottom of thread tl;dr Bike died on me, has low compression, going to rebuild top end. See pictures. Could this be a timing issue also? Does anyone know if the lines on the camshaft sprocket are supposed to line up with the horizontal lines on the head? Thanks in advance for the help! Pic 1- TDC at || https://imgur.com/QJXXjXH Pic 2- || mark https://imgur.com/v7dBSf8 Pic 3- TDC at |F https://imgur.com/DZCPBaT Pic 4- |F mark https://imgur.com/JbcVYhF Pic 5- Engine wants to spin to this position: Cam sprocket lines horizontal with head- https://imgur.com/S3rPRgd Let me know what you guys think. Has my timing jumped? I appreciate your help! Cheers, Spencer Edit: Finally found the damn "T" mark. Always spins past so I wasn't able to see it before. Updated picture posted near bottom of thread. Timing looks fine so just going to rebuild top end next week to restore compression
  17. Hey all! I have a 2011 Gio X31 250cc that is losing compression gradually. It had amazing compression when it was new...but now it's becoming a tiresome task to kick-start when my electric start is down. It's burning a small amount of oil, but I don't even have to top it up between oil changes (~10 hrs. per change). I'm thinking it just needs a valve adjustment to bring the compression back up. I'm surprised how good this engine has been. I ride it hard and it keeps up with bikes 2-3x the hp and refuses to die! I don't know how to adjust the valves on a 4-stroke, let alone a Chinese one. If any of you know how to adjust the valves on a Gio X31 250cc I would appreciate the help! Do I need to pull the engine for this? Thanks
  18. Sunflash

    RTW 470

    So I have done lots of searching but can't seem to turn up the info I am looking for. So after a 25,000 mile run from Deadhorse, AK to Yaviza, Panama and back to my home in Alaska on a Rally Raid Level 3 CB500X..... I am now going back to my roots and picked up a 2004 DRZ 400 with about 2900 miles on it. Lots of reasons for it but the cut it short I know I was looking for something different for the rest of the ride around the globe. So my plan is to build a bombproof DRZ that can take me everywhere and back. To that effect I have already ordered an Athena 440 kit, will be going with the Hotrods +4mm crank kit, and the ACT wide ratio gears. Where my plan differs from most of the other power mongers is that I want to keep the compression low enough to run low regular fuel without going nuclear. That type of tuning runs a bit contrary to everything I can find info on. So who out there has done a low comp 470? Since the plan is a mild state of tune rather than the usual fire breather everyone else is trying to build does anyone have a good recipe for the spacer or gaskets to keep the compression low enough? Cams for the milder state of tune? FCR 39 going to be enough carb or should I be looking to the 41? My engine building has been limited to old air-cooled 4 cylinders and for max grunt not longevity on crap fuel. Lots more will be done to the bike but the motor spec is one of the ones leaving me a little out in the cold. Want the grunt of a bigger motor to pull the wide gears but not the short life of a rocket ship. Thanks for the help.
  19. Before I put my 05 CRF250R away for the winter it was running weird. I noticed it was leaking oil out of the engine cover. It was understandable because i had just put a new stator in. The bike had been running oddly for some time before i realized it was leaking. I just took the bike out for the spring and now it doesn't even start. I bought a new engine gasket to try to fix the leak. I am currently installing it. I am wondering if the low compression could've messed up the top end? I rode it with low compression for about three weeks before it started to bog so bag i couldn't ride it anymore. Will replacing the seal fix my issue or have i created a whole new one?
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