Stock 400EX octane needed?

[MAKO19]

I don't have an owners manual and was wondering what Honda recommends using as far as octane in a bone stock 400EX? I have been using 87 and the bike seems to run fine.

Thanks!

[Speedy 400ex]

it says 98 on one of the stickers on the front of the frame. But I use regular to and im ok.

[08ltRse77]

98? u meant 89

[MAKO19]

89 is what I was thinking. 98 is race fuel octane. I appreciate the information.

[mittman]

i thought mine said 93 but not 100% sure since gas went up ive been running 87 its been 4 months and its running great

its supposed to be a minimum of 92 octane

[atvmaster0927]

I run 93 and its runs excellant.

[billyboy93]

it says minimal of 91 i run premium that is 93 it runs great on it

[UNBROKEN]

i use 93 but had to use a full tank of 87 and i have a 10/1 piston and she didnt knock

[Hondamaster5505]

:eek:

I've been using 87 since I bought the damn thing.. And the guy before me did also...

But, she runs great! I never even knew that you were supposed to run higher.

If i ran 92/93, do you think it would run better or make a lil more hp?

[Speedy 400ex]

Originally posted by 08ltRse77
98? u meant 89

yep thats right. my bad

[trx400EXtreme]

mines an 02 and it's been on 87 it's whole life(exept for some av-gas at the dunes). it runs fine.

[03mach]

i like the knock when i run diesel fuel in it. :D

I ran 87 on accident and i deffinately felt a loss in performance. It wasnt a lot but I felt more of a bog and not as snappy. Ran the tank out put 93 in it and it ran fine. Everything was stock besides the choke plate taken out.

[TRXRacer1]

Anyone that knows anything about fuel will know that unless you have added heat and pressure you don't need added octane. 87 is perfectly fine for stock 400ex's and most of them run it.

[greenblood01]

I believe there is actually a sticker, or it is stated in the owners manual that the 400EX calls for no less that 98, yes 98 not 89 octane. This makes no sense due to the fact that it is only 9 to 1 compression. I have an 11:1 Wiseco piston and I run 91 straight out of the pump with no problems.

I work at a Honda shop, and our shop manager pointed the 98 out to me, and we discussed how it made NO sense, when a YFZ is 11:1 stock and calls for 93 or above...

my manuals say "run a minimum of 92 octane"

[mittman]

Originally posted by 03mach
i like the knock when i run diesel fuel in it. :D


lol i run the off road diesel in it and i get about 300hp haha lol

[greenblood01]

Maybe I'm wrong, but I'm almost sure that there is a sticker somewhere that says 98 Octane.. but once again maybe i'm wrong.

[Speedy 400ex]

ya that is the emssions sticker on the front of the frame. it confused me to.

[red_rider_069]

yea i was running 89 on mine since it went up.. but i run mix now with big bore.. thats fien for stock

[greenblood01]

Originally posted by Speedy 400ex
ya that is the emssions sticker on the front of the frame. it confused me to.

Ok, good. I was starting to doubt myself lol.