Maintenance & Technical > KX500 Original

need help with head gasket

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5dracing:
You might want to check and make sure the radiators and such are not blocked cuasing an overpressure in the system. Are the gaskets blowing out from bore to water jacket or water jacket to outside of cylinder? Kinda sounds crazy, but could'nt hurt to check all passages to make sure they're open.

FIVE-HUNGE:
I had same problem with an '87 500 and '01 500
Tried everything, after multiple head gaskets, cylinder and head resurfacing, and studs. and Not to mention a master machinist (who builds world class drag motors) scratching his head wondering why such a simple dirtbike motor could be such a dilema.
Don't waste your time looking with a straight edge. Just have it resurfaced.
my last try with success was a resurface, OEM steel head gasket, a thin film of Yamabond 4 around the edge of the cylinder and head where it would leak. tourque wrench in the correct pattern and it was a done deal.
Once you get the problem fixed DO NOT REMOVE HEAD FROM CYLINDER when doing top end replacement.
I feel your pain, at it's worst moment I would have a fresh cylinder, head and gasket properly torqued down and coolant would leak out all around the cylinder and head as fast as I would pour it in the radiator. It's enough to to drive you to smash the motor with a sledge hammer and buy a new bike. The only thing that kept me comming back was the thought of the evil grin that appears under your helmet when you twist the happy grip..
nothing satisfies like the KX500 when in good working order.
good luck

KXcam22:
The K5 must be finicky in that respect or possibly doesn't have the best factory "flatness".  Given the type and thickness of the head gasket I'm suprised that they would leak easily.  On some engines it doesn't take much to seal. On an RD350LC roadracer I built, the heads were milled, then lapped to the cyl with valve grinding compound. It used NO head gasket, only a smear of RTV.  No leaks.  If you don't want to resurface the K5, lapping does a great job and it's easy to see your progress by the pattern.  Got to pull out all the studs though, no fun. Cam.

2001KX5:
Cam can you give us more info on this lapping you speak of?

All I know is orings are the bomb! But we ain't gots any :(

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