fuel ?'s

[400exrider_88]

i have a 426 11.:1 compression piston, what happens if i run octane 87 or 89 and not race fuel? also, what does it take to convert a 400ex to E85? not that im doing that, just need it for a paper im writing on ethanol fuels

[zrpilot]

I can't help with the E85 question, but running 87 or 89 octane will depend on alot of things in an 11:1 engine. I would EXPECT it to detonate, but only riding it under your conditions, with the gas that is available in your area will tell.

[lorenjr83]

do you have an after market cam in there with your 11:1 piston?

like if you had a HC stage 2 cam and an 11:1 piston your compression wont actually be much more then stock due to the valve being open a little longer during the compression stroke. so 87 octane gas should run fine.

on e85 you will need to fatten that pig up alot. bigger main jet and not to mention loss of milage

[400exrider_88]

i have a stock cam now, i havent even ran a tank of 87 through it since i got it. had race fuel ran in it before that. im working on the top end now, gonna prolly put a stage 2 in it, i can get that cheaper than a stock cam through a shop i know

[sprayedgt]

Not meaning to high jack the thread but are all the 400ex engines the same? My owners manual for my '08 says to use minimum 91 octane.

[Jnblaster05]

all the owners manuls say use a min of 91 which i would always use 93 if u have the option and as far as e85 gos i thought someone did a really nice write up on how to do it try searchin for it.

My STOCK engine ran crappy on 87 when i accidentally put it in. I would high recomend to put a MINIMUM of 92 or 93 octane in it.

[krt400ex]

Originally posted by sprayedgt
Not meaning to high jack the thread but are all the 400ex engines the same? My owners manual for my '08 says to use minimum 91 octane.


they all say that and all the engines are the same. i run premium in mine no matter wut and i am running stock comp