Head leaking after top end replacement

After changing my top end (03 YZ250), and using a Cometic gasket set, I've noticed a tiny little leak at the head. It's just broken in, with like 1/2 hour on it, and I have not re-torqued yet. It's a really small leak, probably just enough to drip down the cylinder and make a little puddle on top of the cylinder intake, probably less than 1 ml. I cannot tell yet (haven't pulled the tank yet) if it's coming from the gasket area or from the copper head washers.

My question is this... I've got a trip coming up soon, and need this thing working right, so think a re-torque will seal it up? If not, should I get OEM O-rings and new copper washers?

Getting a little frustrated with all the work I've had to do on this bike this year...

Fresh gaskets and another go will prove it is not the washers/o'rings etc. Sometimes everything works right the first time, sometimes it doesn't. Check for debris and burrs in the o'ring grooves while you're there. Then check again.

mechanical version of measure 85 times, cut once....

You'll get it. Just take your time and check everything as you go; haste makes waste.

Fresh gaskets and another go will prove it is not the washers/o'rings etc. Sometimes everything works right the first time, sometimes it doesn't. Check for debris and burrs in the o'ring grooves while you're there. Then check again.

mechanical version of measure 85 times, cut once....

You'll get it. Just take your time and check everything as you go; haste makes waste.

agreed 100%

Does everyone replace those copper washers every time, or just reuse them? All of the how to's and videos I saw people always reuse them. I know the manual says to use new ones, but I was getting the feeling that might not be needed.

I reuse those washer, my 125's head leaked a bit after my rebuild, I re-torqued after 1-2 hours and it never leaked again.

i reuse them a few times but always new orings and gaskets

Copper gaskets can be reused, but you have to anneal them (make them soft again, as they become work hardened) heat them with a propane torch in a dark room until they are a medium red, them drop into cold water. Nice and soft and ready to use again. You can get about two uses for each anneal, then toss when they need a fourth.

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