How much compression is too much?

[Tom TRX250R]

I have always ran around 220psi in my R but recently my friend had his head shaved and trying a CR head gasket with 275psi. I thought that was too much, can't say I have heard of someone running that high of compression. He plans on either running 114 or 118 octane. Will this be suffiecient for a reliable motor or will it be a ticking time bomb? Also do you guys think the octane is high enough considering I am about 200 ft. above sea level, I think?? In the midwest to give you a better idea. Thanks in advance. Tom

[C-LEIGH RACING]

At 275, just think what that poor little wrist pin, pin bearing & crank are going through, man I get skidish at anything over 220.
If he's going to run it like that, better keep a big fat jet in it & dont turn it over 2000 rpm, any higher than that,,,TICK,,,TICK,,,TICK.
Neil

[Rich250RRacer]

Originally posted by C-LEIGH RACING
At 275, just think what that poor little wrist pin, pin bearing & crank are going through, man I get skidish at anything over 220.
If he's going to run it like that, better keep a big fat jet in it & dont turn it over 2000 rpm, any higher than that,,,TICK,,,TICK,,,TICK.
Neil

I don't think the wrist pin is going to be a problem, I WOULD worry more about the rod itself, but I think it should holdup as long as it's stock. I question the strength of the aftermarket rods, like Hotsrods. A close friend of mine runs microsprints with CR motors and that crank assembly holds up pretty well with compression in the 275-280 range, and it's on alcohol.

[sandspanker]

:) I dont run anything over 200 psi. it will run for a long time. I can get about 2.5 years of hard riding. out of mine befor the pistons skirts start cracking.:p

[MR.BIG]

Too much compression will blow the crank seals out of it and it won't be very reliable. When I use to race flattrack our bikes were only pushing 185psi!