07 YZ450F Blowing oil out valve cover breather tube

4 replies to this topic
  • crj900pilot

Posted January 12, 2016 - 06:19 PM


My YZ540F started blowing oil out the valve cover breather tube so I had the cylinder honed and put in a new piston and rings and valve seals thinking blow by. Now its blowing out even more. I had a puddle after 16 sec of running. Any ideas???  Thanks

  • grayracer513

Posted January 12, 2016 - 09:05 PM


Oil overfilled?

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  • crj900pilot

Posted January 18, 2016 - 02:05 PM


Its def not over filled. Anyone ever heard of a cavtating oil pump doing this?

  • drtrcr400

Posted January 18, 2016 - 06:23 PM


As long as the oil isn't over filled you still have blow by. No two ways about it.

Edited by drtrcr400, January 18, 2016 - 06:25 PM.

  • grayracer513

Posted January 18, 2016 - 09:15 PM


Its def not over filled. Anyone ever heard of a cavtating oil pump doing this?


Not cavitating, no.


Check this: If the dip stick is loosened or removed, will oil come from the dip stick hole? 

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