at what compression will you have to....?

[yellow400ex05]

run race gas on a z400.. what gas do you have to run for a 12:1 compression piston and for a 13:1 compression piston?

[pro-rider46]

12 to 1 is about the limit for pump fuel. and 13 to 1 needs some racefuel. you can mix it too. my friend mixes his 50/50

[tar]

I have heard that 11.1 is the border everything above requires atleast a mix

[pro-rider46]

my brothers r6 has i think 12.2 to 1, and runs pump. the best way to tell is to have a knock sensor to see if your getting det. also other things go into play with this, it also depends on what cam you have as well

also depends on the quad its for. I know for a fact that on a 400ex higher than 11:1 will almost 99% of the time require you to run mixed and when you get higher up full race. My brother accidentally put something like 107 octane straight race gas into a little stock polaris phoenix not knowing. funniest thing... it shot flames out of the silencer all night about a foot long no lie

[Aceman]

You guys need to realize octane requirements are different for air cooled vs. water cooled engines. Generally, water cooled can get away with slightly higher compression than an air cooled.

[trx400EXtreme]

^yup^. just because some motors are 12:1 stock and you can run pump gas doesn't mean you can run pump gas in a 400ex with 12:1.

[yellow400ex05]

i know that theres a difference between the two party because of the liquid cooling. My friend ordered a high comp piston for his quad which i s in the shop being fixed and he never even asked what kind of compression piston they ordered..:ermm:

[400exrider707]

Stock z400's are already over 11:1. I would say 12:1 as a rule of thumb for pump on a liquid cooled engine, and 11:1 is the limit on air cooled like the 400ex. This does not apply to each and every one. Jetting, elevation, humidity, temperature all play roles, and each and every motor is different.