ZY Timing/Valve Clearance Question...

3 replies to this topic
  • dangler

Posted November 28, 2002 - 03:09 PM


I'm sure someone here can help me out with this....I changed my '01 WR426 to YZ timing, and while I had things apart I decided to check my valve clearance. The intake checked fine, but the exhaust seemed a little tight(after the timing change). Does changing the exhaust timing affect the valve clearance at TDC. I would assume it does change the clearence since you are changing the position of the cam. If it does, can someone give me the YZ spec for the exhaust valve clearance? Thanks for the help....

  • Hick

Posted November 28, 2002 - 06:30 PM


As far as I know the clearance should be the same, I've done some maintenance on WRs and just used the YZ spec., it never occurred to me that the clearance would be different.

You check the clearance with all the valves closed, if they weren't there would of course be no clearance, so you should be well onto the lowest part of the cam lobe.

I can see what you are thinking though.

What is the clearance spec for the exhaust printed in your WR manual??

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  • dangler

Posted November 29, 2002 - 06:33 AM


Thanks for the reply Hick

I think you are right after giving this a little more thought....the clearance should be the same because the valves are still closed, even after rotating the cam one tooth. I think I was just hoping things were OK and didn't need adjusting....Oh well, wishfull thinking I guess. The WR spec in the manual calls for .10-.15mm clearance for the intake, and .20-.25mm for the exhaust. I could force the correct feeler gauge under the cam (exhaust) but it should go rather 'easily' shouldn't it? The intake seemed much easier, hence I would say they are OK. I guess I should let the dealer do the first adjustment just to be on the safe side....Thanks again for the help.

  • Hick

Posted November 29, 2002 - 02:04 PM


The WR spec in the manual calls for .10-.15mm clearance for the intake, and .20-.25mm for the exhaust.

That's same as in the YZ manual.

I think the exhaust valves go out of spec. a little quicker than the intake valves, so there's nothing out of the ordinary in what you found.

If you can change the timing and check the clearance you could easily change the shims yourself, a small magnet works great to lift the buckets off the valves and will prevent you from dropping a shim. I think it is a good idea to check what shims you have if you are changing your timing, since you have to have the cam out of there anyway, that way you can go ahead and order the next smaller shim size and be ready when they do go out of spec.

If it is pretty close I don't see any harm in riding it a few more times anyway...


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