Hitchcocks Forum

put a new top end on a 2004 500 that I picked up that wasn't running. pulled the head and cylinder off and the top end was trashed. put new barrel, piston and head on it. it runs, but there is a leakage of oil at the exhaust port where the exhaust pipe fits in. is this a problem, and if so where do I go from here.

Is it coming out of the exhaust port or running along the fins near it? If it's coming out of the port it'll probably be something to do with the piston rings, either they're not on the piston the right way up or perhaps not gapped properly. Is the piston the right size for the bore? If the oil is running along the fins it's probably leaking from the head gasket where the pushrods go through, re-make the joint with a new gasket and add some silicone sealant to the joint.

REgards, Mark

small amount weaping out the exhaust port. piston came with rings on it with "matching" barrel. could it be that the rings haven't seated, or am I being too optimistic?

how many miles since the rebuild?

none - noticed it when I was setting the timing and adjusting the carb

the plug looks like it is burning some oil as well

It does sound to be piston/rings/bore clearance related I'm afraid. The best approach is to take it apart, no sensible diagnosis can be made until the parts are cleaned, checked and measured.

REgards, Mark

I'd run it for a bit and see if it beds in.

Most new piston cylinder and rebore will use some oil, just ride it for a couple of hundred miles and it should bed in, DON'T use semi or synthetic oil or it will take forever.