HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
schecter_06

YZ426, cam wear in cylinder head

8 posts in this topic

Hey, I'm in the middle of doing a valve adjustment on my YZ and the cam shaft looks like it burred the cylinder head very slightly between the middle and right lifters. I was wondering if it could be from a clogged oil hole, and if so, how do i check?? Also, would it be alright if i got rid of the burr with sandpaper?

Thanks!

Share this post


Link to post
Share on other sites

Whip out your manual and check the camshaft to cam journal clearance with Plastigage per the published procedure. Single random scores are usually the result of a foreign particle in the oil. Wider scuffing could be an indication that the cam tried to seize. Use your best judgment as to whether to dress up any rough spots. If it's just a groove, leave it. If it has a rough edge, then a little careful sanding may be in order.

Share this post


Link to post
Share on other sites

valvae clearance is out of spec by .03 on all intake valves, on exhaust clearance is in spec. It is the stock cam. The wear on the cylinder head by the cam is preventing the removal of 2 of the lifter buckets, so unless I get these burrs out with the lifters in place, I can't reshim to get back into spec. The wear is on both edges of the middle resting groove for the camshaft, which almost leads me to believe the oil hole may have been or may still be clogged. Can I blow this hole out with compressed air to clear any possible blockage? Is there another way to clear a clogged oil feed hole? I will check the cam to cylinder head wear specs like the manual says, but I still need to make sure it's not going to wear anymore.

Share this post


Link to post
Share on other sites

There is a single entry point for top end lube at the right rear of the head that comes from the external oil line. It flows around the intake cam and then onward to the exhaust cam through passages in the head. The oil gets from the right end of the cam cap to the center bearing area of the intake cam by way of a passage in the cap itself. If the passages in the head were obstructed, the exhaust cam would also have suffered.

On the lifters, normally, you can grab them by the upper edge and pull them out with a pair of needle nose pliers, carefully, of course. Another method is to "bounce" them out past the burrs by tapping on them with a small plastic mallet or a piece of wood and a hammer. As the spring rebounds, it may bounce the lifter up beyond any burring. Again, be careful.

Share this post


Link to post
Share on other sites

I ran into this on mine, seems that the prior owner over torqued the caps. I had to scrape away the mushroomed aluminum and then dremel down the edges. Even with that damage it still runs like a champ....Yami's are tough. I'm going to ride it till something goes then get a new head/cams.

Share this post


Link to post
Share on other sites

Yeah, well I'm not sure if those openings in the cam cap can clog, I know that that's what you meant and not the main oil hose into the cylinder head. Maybe someone else can answer that. And I agree with sharpmarble, though it'd be worth a try to bounce them out first, but even doing that may score the lifter buckets if the score in the cap is bad.

Share this post


Link to post
Share on other sites

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
Sign in to follow this  
Followers 0