Hey WY5,
First I have to ask you , where are you from in Wyoming? We might be near enough to go for a ride!
Anyway, about the head gasket, my 1990 KX5 had the thin steel shim gasket when I bought the bike. When I redid the topend shortly thereafter, I went to the standard thickness fiber gasket to make sure there wouldnt be any leakage that older KX5's are somewhat known for. Afterward, there was no discernable difference in power. I would have to say that if you want more oomph from the green bike, try increasing the airflow through the motor via a pipe/silencer combo or the V-force reed cage. I have both on my bike and they do indeed help. At 5000 ft elevation, my KX5 would run fine on our 85 octane from the pump(with standard head gasket and head milled 0.010") However if you have it jetted perfectly, you may want to run the high octane from the pump for insurance against detonation.
If you want to get in touch to talk about the "Big Green" my E-Mail address is gconner77@yahoo.com
