Race fuel

[440EXR]

This may be a dumb question but when you run race fuel instead of 92 octane do you have to re jet or make any mods or can you just go ahead and use it

[VegasEx'r]

You don't have to rejet to use it, but unless your compression ratio is over 11:1, you'll just be wasting your money.

[Maryland 400EX]

From my experiences with Cam2 (20 years) I can tell you that the machine will run a bit lean with the race gas. To be on the safe side I would go up 1, maybe 2 jet sizes on the main jet to richen up the fuel mixture.

[Wheelie]

No need to rejet when running a higher octane fuel, pour it in and go.

[ChadEXer]

You dont need to rejet for race fuel but like Vegas said, if it isnt above a true 11:1 ratio you really dont need it. If you are just wanting to help your motor run a little cooler and add a little lead(good for it)then I would reccomend running a half and half with pump gas and maybe some VP Red or something like that!!

[440EXR]

Thanks guys think I will go with 1/2 and 1/2 suggestion Im not looking for extra hp got lots just heard it helps the engine run cleaner. I did try it ( straight race) on the practice track the other day and it started to sputter on accellration but the i noticed my head gasket was leaking(black around the gasket area) so I was losing compression guess that was the cause. yea expensive is right $65.00 Cdn. for five gallons ouch!!!

[bansheeguy77]

race fuel smells good....but like they said it does nothing unless u have the right mods....o and hey maryland 400ex can i have ur hayabusa :D

[Jeff]

My friend runs Jet Fuel in his....

[Maryland 400EX]

Let me clarify a known fact about race fuel. In a low compression stock 400 EX motor such as what we are working with, race fuel is not beneficial I agree... In fact, the rule of thumb for best performance is to use the LOWEST octane fuel that doesn't cause detonation in a given motor. But for those who love the smell of high octane gas such as myself and absolutely HAVE to use it, these motors WILL RUN LEANER with Cam2, VP-C12 or whatever. Therefore, I recommend to stay on the safe side and raise the main jet one size for safetys sake and to prevent a lean condition inside the combustion chamber. If a given 400EX is running a tad lean before using the race fuel that particular engine is going to starve for more main jet with the fuel. Guaranteed! Especially near or at full throttle. This particular scenario can burn a hole in the piston. Trust me, I've been using this stuff for years.

[VegasEx'r]

Originally posted by Maryland 400EX
these motors WILL RUN LEANER with Cam2, VP-C12 or whatever.

I'm just curious, what is this based on? I'm not trying to start a flame or anything, just want to know.

[ChadEXer]

Im kinda wondering the same thing myself????

[Wheelie]

Do tell, inquiring minds want to know.

What about aviation fuel?

[Maryland 400EX]

Well, to be honest what I have told you guys is no secret. Anyone who has spent time around this stuff can give you the same info. I've spent the better part of 25 years around race gas with cars and bikes, both carbureted and fuel injected. The last ten years I've spent time tuning bikes with the help of dynos and I've seen the Air/Fuel Ratios with and without race fuel. Now to get to the point, you ever wonder why some guys post that "after they installed the race fuel their quad hesitates before it goes" or that "Their quad felt like it lost torque" with the race gas? The answer is that they're encountering a lean condition which actually causes a slight loss in performance. Once more fuel is added, whether it be through turning the airscrew, raising the needle or installing a bigger main jet, they make MORE power. It seems so silly for me to try and prove my theory because this is so much a "No Brainer" but oh well... Even with my Hayabusa I go to the track with my tank half full of Nutec (90 octane oxygenated fuel) and if I try and race with the fuel computers settings for pump gas, the bike runs lean and doesn't have the gusto like it does when I add fuel through the Power Commander (5%). It's a night and day difference in perormance. The same principle goes for the 400 EX but to a lesser degree since this thing is very low on power.

Just a guess!

Cam2, C-12, etc. probably have a higher density (specific gravity) than pump gas thus there needs to be a tad bit more fuel available to enter the intake air stream. Or conversely, slightly increase the air speed through the venturi to pick up the heavier race fuel.

I don't know but it sounds good! :D

[quadman21]

440EXR, out of curosity, you mentioned that your head gasket blew. What head gasket were you using? I also had my head gasket blow on my 440. I had only had it a day when it happened. I found out that the guy who done it for me stripped the clyinder stud threads. I have since fixed it myself but used a cometic Fiberglass (or whatever you call that material) gasket and have had no trouble since.
Maryland 400EX, I'm running sunoco 114 mixed 50/50 with my mild 440. I'm pretty sure it isn't a true 440 cc from what I've read about the quench area and so on and so on. I have posted before that it seems flat on top end. My exhaust color is a greyish white and I have my main jet two sizes larger already. Would raising my needle help me out?

[Maryland 400EX]

Quadman, raising the needle will richen the midrange while going a size larger with the main jet will richen the upper rpm range. I would recommend that you take the quad out and run it wide open for 5 seconds or so then shut it off while still holding the throttle pinned. Immediately get off and check the plug color.This will help you determine by a spark plug reading whether or not you're getting enough fuel via your main jet. If the plug looks okay after that test then you may want to fine tune it by raising your needle a maximum of 1/2 to 1 clip because your lack of power through being too lean is in the midrange and not the main. If the plug looks whitish then go with a larger main. I put the 110 Octane Cam 2 in my EX yesterday and noticed a slight power loss throughout the powerband. The quad had a slight hesitation of idle and didnt really pull with gusto as it once did with pump gas. I'm going to raise the needle 1/2 clip by installing a small washer under the e-clip on the needle (Old school trick), this way it won't be as drastic a change as going a whole clip down. I'll take the quad out a test ride it, then I'm going to go one size up on the main jet as well. This should slightly richen the whole rpm range a hair to get the Air/Fuel ratio back to where it was. Lastly, there's also the option of richening the idle with the airscrew if there's an erratic idle but currently I don't have that problem.