What should I Check? Carbon on Plugs.

That was my comment. I was hoping that it was something else. But the motors got 10,000 miles on it so its due to adjust valve clearance. I'll be out buying a gasket and shims soon

Before you buy any shims check the valve clearances. I have only changed one shim in my KZ650. That was in 1977 on one of the intakes at 500 miles and that was only because it was near the tight limit from the factory. Since then, with 48,500+ miles, the valve clearances are still within spec. The shim under bucket design really works great, other than the PITA when you need to change a shim. So unless you have a bunch of carbon build-up or something else unusual going on in the head, at 10,000 miles you may be very pleasantly surprised at how little the valve clearances have changed. Ed

"Checking" clearances is the easy part, whereas "adjusting" clearances by changing shims gets more involved.

Perhaps merely checking the clearances will find them still within specs, which is helpful by ruling out too tight clearance as a possible cause of plug fouling due to loss of compression especially at normal operating temperature.

The reason it's necessary to assure correct valve clearances in addition to testing cold compression is that compression psi may be within specs with too tight valves barely sealing while engine is cold, but the too tight valves begin leaking when the engine reaches normal operating temperature.

Good Luck!

[650ed beat me to it!] :laugh:

I was going to check clearances first and then buy the nececary shim. Off the top of your head what is the intake and ehaust clearances. My books out in the garage,?Thank you