any of u run 87 with no problems? if it needs it guess i'll use 93....but ouch!

 

If you go up in altitude, then you can get by with less octane, but at 5000 ft and lower, you should use 91.

 

<div class="FTQUOTE"><begin quote>Originally posted by: hondabuster

If you go up in altitude, then you can get by with less octane, but at 5000 ft and lower, you should use 91.</end quote></div>

I went and got some 93 they sell 87, 89 & 93 around here.

guess thats what I'll run.

 

If compression is 9.1-1 or less you can run 87 octane. I've ran 89 octane in mine (11.3-1) and no problem.

 

yeah, i'm not sure on the compression ratio of the 400ex I wouldn't imgine it's all that high... maybe 10 to 1 at the most.

 

Have you read your owner's manual??? I don't know about the rest of you, but my manual, says 92 octane or higher!!!

I run 91 pump gas with Klotz octane booster. That makes me 93.5 octane, for a little hedge against detonation. The booster has fuel preservative and an ester synthetic lube for the top end...so that is all just fine with me.

This engine is air cooled, so it can run hot sometimes. Best to run a little higher octane as insurance against any detonation!!!

 

i agree. in my raptor even i run stock comp and i run 3/4 91 ocatne and 1/4 vp red 110 octane. the way i look at it is better save than sorry. a rebuild on a 4-stroke can get pretty expencive. not saying you need to run vp race gas but i whould get atleast 91

 

yeah i put 93 in it today as the first refill from what the dealer put in it (they prob put 87...)

i was just used to pouring 87 in the ole 300's haha. i was like 91 or higher ur kidding me!

 

With any off road motorcycle or quad it is very difficult to hear when it begins to ping. Often this can occur when you are not exactly in the correct gear and the motor lugs slightly. This is reason you should play it safe and only use 91 or better.