HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
joelenway

2001 yz426 feels like no compression after rebuild I'm stumped

22 posts in this topic

OK so I had my crank rebuild new cylinder new piston put it all back together and I can push the kick start with my hand.. timing is on I and dot aligned with the head. I put a teaspoon of oil in thei plug hole kicked and kicked but no resistance.. valves were cleaned checked everything was in specs.. where do I go from here need help!!!

Share this post


Link to post
Share on other sites

Just to be clear.  Is the crank turning and is the spark plug in?

Share this post


Link to post
Share on other sites

Yes spark plug is in. And yes the crank is moving..it has spark it has gas but I but I can push threw the strokes with my hand it's that easy. It feels the same kicking it over with the spark plug in or out..

Share this post


Link to post
Share on other sites

Check your decompression cable and make sure it is not too tight and holding the valve open. Other than that I would suspect the valve timing is off.

Share this post


Link to post
Share on other sites

The cable is very loose and when I kick it over I can feel the Decompression lever Get Harder And softer.. Could It Possibly Be 180 Degrees Out Of timing? But wouldn't it still be hard to kick over I mean it feels like I'm kicking it over without the spark PLUg In Its That easyeasy

Share this post


Link to post
Share on other sites

No compression has to be one of two things, air leaking past the rings or the valves. Assuming there is not a gigantic hole somewhere, the valves are the  most likely culprit. It's easy to get the timing off enough to cause serious headache's. I always check TDC with a probe of some sort just to be sure and double check that the cam lobes are pointing away from each other  when you have the marks aligned with the head and that you are looking at the correct marks.

Share this post


Link to post
Share on other sites

That decompression setup is where I would start - check it out end to end.

Share this post


Link to post
Share on other sites

Do you have exhaust cam lobes pointing to the front of bike and intake cam lobes pointing to the rear? I have Hotcams and got confused on all the alignment dots.

Share this post


Link to post
Share on other sites

Take some pictures of the of the cam timing marks to show us.  Also, drop a chopstick or something down the spark plug hole to make sure you are at TDC and make sure the bottom marks line up per the manual.

Share this post


Link to post
Share on other sites

The dots don't line up exactly with the head. I moved it one tooth and it was worse the other way. So that is as close as it gets

Share this post


Link to post
Share on other sites

I have not got it started since I put it together.. should I keep kicking it to see if it starts and maybe the piston will seat??

Share this post


Link to post
Share on other sites

Don't really know what happened but said screw it I'm gonna put it back together and bring it into the shop. Got it all together kicked it one tim it ztarted right up.. LMFAO!!! TIME to break it in..:)

Share this post


Link to post
Share on other sites

Correct me if I am wrong, but it looks like you have a decompression cam? Why do you have the decom. lever still?

Share this post


Link to post
Share on other sites

When I bought the bike the guy told me even with The decompression cam he needed the lever to start it.. well after I rebuilt it obviously it doesn't need it and I don't have a plug for it so I just left it.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0