2002 YZ426 crankcase cover damage?

I removed the right crankcase cover of my 2002 YZ426 to replace the water pump impeller shaft (impeller would not unscrew). I noticed that along the top inside rim of the cover there was what appeared to be a machined groove, or more of a band of metal that was machined off. I assume this was caused by the clutch. I'm the second owner, and have no idea if the clutch has been replaced and perhaps installed improperly. The machined area looks to be about 4" long x 1" wide. Has anyone ever seen this type of thing? Thanks for your help. I've never tried to attach urls to images, but the urls are as follows:


A close-up of the area of damage is at:


The "machined" area is silver, and the normal areas are darker grey.

That looks like it was done at the time of manufacture. Cast cases are often fly cut like this for additional clearance. These are made in permanent molds, several at a time, and it's just more cost effective to correct the ones that need it, rather than scrapping an entire set of molds.

my case is like that too, i wondered if maybe the clutch was rubbing or something, but it dosent make any noise, no shavings in the oil, so i havent worried about it too much

Mines got it too, and no problems.

Hi Guys,

I sincerely for your replies. This forum is great.

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