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Drav

YZ426F lockup..need help!

5 posts in this topic

Im completely baffled. The kickstart was locked up like the motor was seized, so I took off the valve cover to check the chain and such...when doing this, I was able to move the flywheel multiple turns back with the socket wrench, I can turn it clockwise for as long as I want without it locking up, but CCW it will always lock up at the same point, flywheel or kickstart. For example, if I move the flywheel CW 8 turns, I can kick it down to that 8 turn point then it locks. Cam timing looks a little off, would that cause this?

It's not seized obviously since everthing moves fine CCW so I dont even know where to begin.

I can get some video of the issue later.

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Im completely baffled. The kickstart was locked up like the motor was seized, so I took off the valve cover to check the chain and such...when doing this, I was able to move the flywheel multiple turns back with the socket wrench, I can turn it clockwise for as long as I want without it locking up, but CCW it will always lock up at the same point, flywheel or kickstart. For example, if I move the flywheel CW 8 turns, I can kick it down to that 8 turn point then it locks. Cam timing looks a little off, would that cause this?

It's not seized obviously since everthing moves fine CCW so I dont even know where to begin.

I can get some video of the issue later.

The manual says to rotate the engine in a counter clock wise (CCW) directon only at the flywheel.

If your came timing is off, you might have a valve hitting the top of the piston.

I'd put it at top dead center (TDC), then check to see that your cam makes are lined up with the head...cam lobes should be pointing out, away from center point between the two cams. If not corrrectly timed once at TDC, then obviously you'll have to release cam tensioner and take a cam cap off and rotate that cam to get it to the right point.

Good luck!

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Update:

It's not the timing, took out the cams, checked the valves, etc etc, everything is timed properly...still locks up once turning CCW to that point so I think it might be the bottom end, I just dont know what...argh this is driving me crazy, I dont have the skill to crack open the crankcase or the money to take it to a shop, thinking about just buying a working bottom end off ebay and swapping over everything else...

Anyone have any ideas?

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Sounds like a big end bearing. Splitting cases isn't a bad job. Just follow the manual and take your time.

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