Aftermarket Crankcase Cover??????

5 replies to this topic
  • joehonee

Posted January 14, 2010 - 07:34 PM


I just bought an 01 YZ426 and was not in love with the way the bike started. I have read all the threads and know the correct procedure but still not satisfied. It seemed like it was time for a carb cleaning and valve check. The problem I am running into is apparantly the prev owner bashed the left side of the motor because the crankcase cover is aftermarket. This wouldn't bother me normally but there are no plugs to access the crank bolt or view the timing marks. Any suggestions????

  • grayracer513

Posted January 14, 2010 - 09:17 PM


One reason you occasionally find aftermarket flywheel covers is that the bike has been equipped with a high output flywheel/stator combo. Find TDC, if necessary, by removing the plug and probing for the piston, or remove the flywheel cover.

  • joehonee

Posted January 15, 2010 - 04:08 AM


Will there be marks behind the cover? I looked quickly last night before I quit for the night and the flywheel looked different than in the manual. Might be one of the aftermarket ones that you mentioned. I believe there is a line and an "H" marked on it. Where will the corrosponding mark be? One the case?

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  • grayracer513

Posted January 15, 2010 - 08:55 AM


Will there be marks behind the cover? ... I believe there is a line and an "H" marked on it.

No marks inside. The "I" and "H" are OEM type marks, so it may be an OEM flywheel.

It may also have had (or still have) an aftermarket weight bolted to it that requires the cover.

  • joehonee

Posted January 15, 2010 - 09:07 AM


So without the factory flywheel cover the only way to assure TDC is via the spark plug hole?

  • grayracer513

Posted January 15, 2010 - 09:43 AM


Yes. However, once you find it, you can place a mark at TDC on the interior of the flywheel chamber to correspond with the "I" mark.

You can also get pretty close by sticking a steel rule on the flywheel so that the edge aligns with the crank center and the "I" mark simultaneously, and then rotating things until the ruler is centered on the cylinder axis.

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