85' 250R Compression Questions

[Turbeau]

Hello all you R experts,

I have been adding upgrades to R and would like some input. I just installed a cool head after checking the squish both before and after installation. The squish is above .058. I think the cool head that I got is older because it dose not have o-ring grooves machined into the head. I am running a CR head gasket with a 22cc dome. I checked compression after installation. The gauge was at 200 psi. My engine builder recommends that I run 110 octane race fuel. What compression have you seen with a stock head using a CR head gasket? What is the highest 250r compression that you have seen?

Thanks.

[yaegerb]

IMO that's a pretty tight squish. Stock is around .090 at ~175-185 lbs of static compression. The tightest I have run is a .050 with static at 221 and I was running VP 110. You are definitely on the borderline. I would perform a UCCR to be 100% sure you can get away with pump gas

Or

Just play it safe and run 108.

[efhondakid]

CR HG? Haven't heard of that how much thinner is it and what year CR?

[bkm]

CR HG? Haven't heard of that how much thinner is it and what year CR?

I always used the 1989 cr250 head gasket. I think 88-91 cr250 uses the same gasket, but I know for sure 89 always worked.

[250rmanfmf]

My 86 TRX 250r has a CR head gasket and my compression is at 200 psi. I am running 110 octane.

[arlaunch]

http://www.macdizzy.com/compress.htm

Here is a link to some information regarding compression ratio vs. octane.