yz426f sudden power loss after clutch replcment

wondering if someone can help, I recently had to replace the clutch basket in my 426 and when I put everything back together went to run it but after about 10 seconds or so it just cut off and now there seems to be very low compression as if the decompression lever is pulled in. could this be piston rings, a sticky valve? I had the rocker cover off for a couple of weeks while waiting on parts don't know If that would make a difference, it was covered though.

Better have the cam cover off again and check the cam timing.  Sounds a lot like it skipped on you.


It's not completely uncommon for a valve to get hung up just far enough off the seat because of carbon on the stem, etc., that it affects compression, either.  While you're poking around in there, check the val;ve clearance.  If you find one much looser than it should be, try gently tapping the top of the lifter with a brass punch enough to make it "bounce shut" a couple of times; that may fix it for the time being. 

thanks man!

I'm fearing the worst for her as I've had 2 strokes go on me so I think I automatically go to piston! I'll check the timing and clearances this weekend and hopfully that will shed some light.

really appreciate the input this is the second time you've helped me out!

OK been a while since I posted in this but since then I have checked the timing and when I line up the line at the crank the dots on the cams just sit ever so slightly off but not really enough for a whole tooth. I'm not 100% but thought the chain was maybe a bit stretched. any ideas?

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