yz 400 engine trouble - aluminum in oil

I have a 99 yz 400 - after a long hot trail ride a couple weeks ago I was quite disturbed to find the oil was full of aluminium powder and flakes. After that I no longer needed to pull the decompression lever to kick the bike over. The engine still runs, but sounds awfull. I don't want to run it anymore, I guess it's time to pull the engine apart and find out what went wrong. Has anyone had this happen, any ideas what parts I might need to replace/repair. I have never pulled it apart, but I have the shop manual. I guess I'm out for the season.

thanks in advance

Chillie

Possibly bearing material from a bad bearing.

Or it could be clutch material. But if the engine isnt running right anymore, then its probably a bearing failure.

Are you sure it's aluminum? If it were a bearing failure the bits and pieces would be mainly steel. Aluminum is far too soft to be a bearing material. My guess (total guess) would be a scored cylinder/piston, and the aluminum is bits of the piston skirt, if of course the piston is aluminum, is it? That could explain compression loss (past the rings) and running badly.

Dallas

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now