compression ratio and race gas

[CR500rider]

I have an 04 and was thinking of rebuilding over the winter, possably stroke/bigbore and higher compression ratio. what is the highest ratio i can go and still run pump gas? Im trying to avoid the race gas issue all together. thanks

[r450er]

12.8:1 JE makes this. Anything over it = race gas.

[pro-rider46]

that je 12.8:1 is only for 06+ 450rs, and that is really pushing the limit, i would probably mix gas for that.

but cp makes a great 12:1, and 12.5:1 pistons for the 04-05 450rs, and 12.5:1 is probably the farthest i would go on pump fuel.

[300extreme#8]

I'm pretty sure that you can run 93 with 12:1 and any higher ratio will need to burn race gas so it burns cleaner at higher temps. Though I know people who have run 93 with 13:1 and it never hurt anything but race gas burns cleaner and its better for the motor bc the higher compression makes it run hotter.

[BlaineKaiser450]

i have a CP 12:1 and it runs great wiht 91

[eastside 400]

race gas has nothing to do with burning cleaner the reason race gas is needed for high compressions is because the higher the octane in fuel=the higher resistance to burn, when you go higher comp, the pressures will want to ignite lower octane fuel spontaneously and abruptly and that is preignition (knock or ping) when u run race gas the higher octane will resist burning until the spark plug fires and normal combustion occurs. 12-12.5 is the highest i would go on pump 93

[pro-rider46]

Originally posted by eastside 400
race gas has nothing to do with burning cleaner the reason race gas is needed for high compressions is because the higher the octane in fuel=the higher resistance to burn, when you go higher comp, the pressures will want to ignite lower octane fuel spontaneously and abruptly and that is preignition (knock or ping) when u run race gas the higher octane will resist burning until the spark plug fires and normal combustion occurs. 12-12.5 is the highest i would go on pump 93

well said

[LoweJ82]

so could I turbo blue racing fuel in my stock 07 450r?

[eastside 400]

you can run it but it would be pointless, you would not pick up power unless its an oxygenated fuel, not sure if that is but i dont think so, and your just wasting money if its a stock motor anyways. you would most likely loose power

[CR500rider]

Originally posted by eastside 400
you can run it but it would be pointless, you would not pick up power unless its an oxygenated fuel, not sure if that is but i dont think so, and your just wasting money if its a stock motor anyways. you would most likely loose power I gave up trying to explain that to people.

[400exrider707]

I think the main point for the weekend riders has been hit. 12:1 is about the highest you want to go safely for pump. Once you really get into the science of it, there are other factors. The machine needs to be jetted for the fuel, especially with oxy fuels, also your cam overlap will play a large role in this.

[LoweJ82]

Originally posted by CR500rider
I gave up trying to explain that to people.

not everyone knows everything so I thought I would ask, more than half the people I see are running turbo blue in there bikes so I figured I would ask and see what kinda response I got, since its a 12/1 ratio I didnt know if it would be ideal or not.

thanks for saving me a few bucks a gallon though if it isnt gonna do anything for me other than smell good.