I want to bump the compression up some on my 85 250r. Running race gas is no problem, I get it free. So anyway, my question is what is a safe amount to shave off of the stock head?

 

I dont know off hand but what i did on my 85 atc250R was take a metal 86 trx250r head gasket which is made up of three peices, two really thin peices of metal and one thick peice in the middle and all three are riveted together. I drilled out the rivets and used one side if the thin metal gasket (it doesnt matter which side you use they are both the same and they will seal off). A thinner gasket bumps up compression. Most people know that the trx came with less compression than the atcs. that is why the trx gasket is made up of three peices because they were trying to make it thicker to lower the compression. while a stock atc gasket is thinner than a trx gasket doing the gasket the way i have described is thinner that the stock atc gasket which will in turn raise compression without milling.

 

Yea, what he said. Thats what I did.

 

sweet. thanks. will i need to run race gas with that set up?

 

If you get above 190 psi. Thats the threshold for race gas in a 250r