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2001EX
07-10-2003, 04:22 PM
Why do you need to run race gas and pump gas mix with an 11:1 piston on a 400ex? My street bike was 12:1 and I only neede 91 octane. Also, my brothers Predator is 10.8:1 and it only calls for 87 in the manual.
Glamis400ex
07-10-2003, 04:26 PM
air cooled versus water cooled.

Glamis
TheX1992
07-10-2003, 04:38 PM
different size cylinders.....the bigger the cylinder (more than likely on your street bike) the less octane you have to use for that compression piston........i think
GNCC#829
07-11-2003, 04:09 AM
Originally posted by Glamis400ex
air cooled versus water cooled.


Thats it!;)
wilkin250r
07-11-2003, 04:27 AM
You need higher octane to keep the fuel from pre-igniting. How would it pre-ignite? Heat and pressure of course. Increase the compression, you increase pressure, so you need a higher octane. Likewise, air-cooled engines typically run hotter than liquid-cooled, so you need a higher octane to withstand the additional heat.
kxrider
07-11-2003, 08:54 AM
my kx used to require 115 octane, ,but i tuned it down cuase i couldnt afford to ride :D , but my friends 250f is 13.1 stock and it required just preimum gas, wtf:confused: