Do I need to Run Race Gas?

[FlattrackR]

I need some expert advice. I'm looking at getting a 400 EX. Its got a 440 kit, 12:1 piston, cam and a DG pipe. My questions are.

Do I need to run race gas? I ran a 12:1 piston in my yz450F, and did not, but I'm not framiliar w/what the big bore honda likes.

Are there any major downfalls to running a 440 equipped EX?
Anything inparticular I need to look at w/these mods?

Thanks Todd

I accidently posted this in the wrong forum the 1st time......

[honda250xrider]

simple answer is YES, anything over 11:1 compression and i would dif. run race gas.

[Foxnake42]

i have a 416 with 12.5 : 1 using 94 and has no trouble at all.

[Quadzilla]

You must be running the standard EX thickness of gaskets, hence 11ish to 1.... XR gaskets would get you closer to what the piston is rated for...


Originally posted by Foxnake42
i have a 416 with 12.5 : 1 using 94 and has no trouble at all.

[Giz400ex]

From what these engine builders say is that higher than 11:1, you should run race gas but you can always run 50/50 and that should be fine. Running race gas straight can get pretty expensive.