Compression Ratio..How High???

[zermatt7]

Whats the highest (safe) compresion ratio yuo can run on a 300ex and still use pump gas...(91-93octane)...?

I read the new yamaha is @ 10:5 to 1.

[K_Fulk]

It varies by machine, but usually between 10:1 and 11:1.

[member]

id just go higher and spend the extra $$ on high octane gas :) i hear there is a big diff. in power

[Aceman]

You go any higher than an 11:1 piston and you will need a heavier connecting rod.

[400exdad]

Stay between 10 and 10.5 to 1.... just run premium pump gas. The newer quads can run higher comp. ratios because they are liquid cooled and can get rid of the heat better.

[zermatt7]

Thanks for the advice....

[hondafox440]

Originally posted by 400exdad
Stay between 10 and 10.5 to 1.... just run premium pump gas. The newer quads can run higher comp. ratios because they are liquid cooled and can get rid of the heat better.

Not exactly. Higher octane fuels are more resistant to detonation, meaning exploding due to the pressure of the piston (like in a diesel engine) instead of exploding when the plug fires. The slight difference in engine temps between an air cooled engine and a liquid cooled engine really won't affect this at all.