With a 440 kit with 12:1 compression do you have to run a high octane gas than 93?

 

we've ran 87 octane into our xr500r bike iwth a 12.5:1 for a long time now, its never really had any objections, except one time it back fired and blew out acarb gasket.

 

anything higher than 11.5 :1 your octane should be increased or you run the risk of pre detonation (knocks or pings) and that could cause some big repairs. but you can run lower octane just might not run as well.

 

Do a search for octane requirements and you will see why 93 in a 12:1 will not be a good thing to do.

 

http://auto.howstuffworks.com/question90.htm copy and paste this all about octane

 

93 maybe. i have a 13.5:1 and i have to run vp's c-12 race gas. you may have to go 50/50 with some race gas.

 

10:1 is the highest compression to go with 93 gas. any higher and your looking for trouble.
at the compression your at and the low octain your using your riding a ticking time bomb.

your going to have to mix race gas. octain booster wont work

 

10:1???? the z-400 comes with 11.3:1 and is rated for 87 octane. 12:1 yes id mix 50/50

 

10:1 is the safest for a 400ex when running 93 octain. but you could probly get away with 11:1 on 93 octain.

 

sorry if that came off wrong. what does the ex come with? ive heard 1 point on compression 50/50 , 2 point race gas. i went up 2 points so 50.50 was not a option.