What octane do you guys use for a stock 400ex i usually use 89 but sometimes use 93 what is the best to use?

 

I would use no less than 92 octane.....that is what is recommended by the factory.

 

check your owners manual, it recomends a minmum of 92 octane.....

Leo

 

I would only run 92 or a little higher, I ran 104 with a little re-jetting, 89 would never even touch my tank

 

Thanks for the info, I'll start running 93 I'll get more power out of it anyway.

 

No - you won't get more power out of it.

If you have a predetonation problem at a lower octane, raising the octane will cure it, that's all.

I have a higher compression piston in my 400ex (10.8:1), and I have no problem running 91-92 octane gas.

If you have stock compression (stock piston), you can probably get away with 87 octane, if not that, then 89 octane for sure.

Buying a higher octane gas than you need just wastes money.

ogre

 

I got around to checking my owners manual and it says to run at least 92 octane.
Thanks for the help.

 

I run 11:1 compression and plain old 93 works good. Sometimes I buy race gas. It is awsome! It runs so perfect, has more power, and runs cooler. It is 116 octane!! Even a 50/50 mixture runs awsome, only prob is it's like 5 bucks a gallon.

 

Oh yes, and what a huge waste of money, a big 'ol 10 cents per gallon, in a 2.5 gallon tank.

I run Premium all the time. Sure, it will run on the cheap stuff, and even though you might not feel the difference, I'm sure it'll run better on the good stuff (crisper throttle response, maybe slightly more power). Plus, ATVs tend to sit around a lot, and the octane rating of the gas drops off as it gets older. So if you put 87 octane in, a month later it could only be 83 octane, which would surely not run as well.

 

Motorhead -

Thank you for your input.

Correct me if I'm wrong, but doesn't an octane slightly above the level of predetonation give you the most crisp throttle response and best power output?

I know your position regarding octane, I've seen your resilient stand many, many times on this board. I do not wish to challenge that.

The point I wanted to make to the other posters is there is a misconception about octane and power. Ever been to an Amoco gas station? How they say "get more out of your car," etc., if you put in 92 octane gas. I always get a chuckle out of it!

ogre