A 2008 KX250Fdepends on the bike, with the 1st gen crf250r motor you can run up to a 13.8:1 piston on pump gas.
oh well damn I don't know, don't think I'll ever know.A 2008 KX250F
We've met before right?.....Why not get a 450?
That is a valid concern.I have never been a fan of putting in high performance anything as reliability and longevity suffer in my opinion. I have a buddy put in high compression pistons in his Harley and then starters began breaking. Stroking and over size are one thing but changing compression is another. I suppose it depends on the amount of altaration but this is just my opinion though.
It makes a larger difference than you'd think. A stock 150F trail bike runs 9.5 to 1Pro Circuit claims that their high compression piston is designed to run on pump gas. However I'm not sure if they're referring to only the 13.8:1 or both. Might have to email them on that.
Still curious on the low end power gains, is going from 13.5:1 to 13.8:1 really even that much?
Our premium is 93-94, think that that'll be enough for at least the 13.8:1?The term "Pump Gas" is misleading, as my premium is 91 octane here in CA where in other states I've seen 94 octane as premium.
As a rule of thumb I say 12:1 and up requires 91 octane as a safe fuel. It's a high enough ratio that a higher octane fuel won't rob you of power, and when your engine gets really hot and hot spots appear on the head/piston, you won't ping/detonate.
Running a high octane fuel in a lower compression engine will rob you of power because the fuel is more resistant to ignition.