cam2 race fuel/93 octane

[81 clark racing]

i have a 400ex with the mods listed in my sig. would it be ok to run 1.5 gals of 93 octane then add 1 gal of race fuel. or will this cause problems like getting to hot not runing right etc. also if i can run it will i notice any gains? thanxs

[GPracer2500]

Your engine doesn't need any detonation protection beyond what 93 provides. It won't hurt anything to run that mix (and there may be some minor advantages to a racing fuel regardless of the octane rating), but you may need to rejet to keep the engine running at it's best. Racing fuels usually require different jetting then pump fuels.

Pretty much, there's no compelling reason to run that mix in your ATV.

$0.02

[81 clark racing]

thanxs. you said i may need to rejet im runing a 170 main 3 notch on needle. so would runing race fuel make it run richer or leaner?

[GPracer2500]

Could go either way. It depends on the fuel.

[REDRIDDER]

81 clark racing did you know this( Fuels- Some common misconceptions about race fuel are: 1. It burns hotter and can cause your motor to overheat 2. It will give your motor more power. 1. Race fuel is a high Octane fuel. Octane is a reference number that tells how much heat the fuel will withstand before detonating without a spark. Octane itself is a fuel similar to gasoline, it was given a rating of 100 to use a reference point to compare to gasoline. The amount of heat produced by a fuel is measured in B.T.U.'s. All gasoline's produce about the same amount of heat so race fuel will not cause your motor to overheat, in fact in most cases it will run cooler (race gas has additives that increase the cooling effect it has when it evaporates, like the cooling effect rubbing alcohol has on your skin). If high octane fuel was more likely to do engine damage they wouldn't use it in aircraft engines 2. Every engine requires a slightly different minimum octane to operate properly. If your motor requires 91 octane and your using 93 octane then it probably wont gain much from 108 or 114 octane race fuel. Most race fuels will require rejetting because the fuel carries more oxygen than pump gas, without rejetting it's possible that your engine will run leaner and produce less power. So why pay more for race gas? High octane race gas allows you to build an engine with higher compression, more spark advance or leaner fuel mixture, without detonating the fuel. The power advantages of race fuel come mostly from these changes. The higher oxygen content means you will run bigger carb jets to get the correct fuel mixture. Your engine will burn more fuel because it has more oxygen available to burn the fuel. Octane is just one of many specifications of race fuel. The specs of race fuel are measured and adjusted to the legal limits according to racing organizations. Every gallon is check and will be the same every time you buy fuel (if the fuel is fresh). Pump gas can vary greatly from one week to the next or from one station to another, and they only check samples of pump gas from thousands of gallons they produce. Different additives are added to pump gas according to the time of year and location where it will be used. In winter they add more alcohol to help remove moisture and they use additives to make the gas evaporate better at low temperatures ("vapor temperature"). Gas that will be used in very hot climates is given additives to lower "Vapor Pressure" to prevent "vapor lock". This is great for your car (especially fuel injected cars that measure and adjust fuel mixture electronically) but for a race bike it can alter your carb jetting from one tank of gas to another. The main thing to remember is to check carb jetting if you run race fuel, also remember if your going to go back to pump gas you may have to switch the jets back. In most cases stock 2 strokes run well on premium pump gas with the proper carb jetting and will gain little from race gas. Unless your building an all out "race only" motor I suggest using premium pump gas or mixing one gallon of race gas to 3 or 4 gallons of pump gas. Whichever you choose you should use it consistently )

[81 clark racing]

REDRIDDER thanxs that just helped me out alot i appericate it. so im going to mix 1 gallon of race fuel to 4 gallons of pump gas and how will i no if my quad is runing to lean? also will i just have to bump up my main jet? i have it at a 170 right now

[400exrider707]

170 sounds ridiculously rich for your current mods, but I dont know.

[REDRIDDER]

Originally posted by 81 clark racing
REDRIDDER thanxs that just helped me out alot i appericate it. so im going to mix 1 gallon of race fuel to 4 gallons of pump gas and how will i no if my quad is runing to lean? also will i just have to bump up my main jet? i have it at a 170 right now post pics of your plug when you mix your gas and use a new plug every time your going to jet .and your welcome

[quad97]

the only thing that may require race fuel with your mods is an advanced timing key and you say it is from curtis sparks? Give them a call and get their opinion and jetting recommondations. 170 sounds too rich to me also. I run a 170 in a z400 with a 500 big bore stroker. also the jet you change is dependent on if it is rich or lean at a certain rpm. main jet is for wide open throttle, needle position is for midrange ,and pilot jet and fuel screw for bottome end adjustment.

[GPracer2500]

Originally posted by quad97
....also the jet you change is dependent on if it is rich or lean at a certain rpm. main jet is for wide open throttle, needle position is for midrange ,and pilot jet and fuel screw for bottome end adjustment.

Close! But you're intermingling throttle position with rpm. The different jets correspond to different throttle positions--they have little to nothing to do with RPM. For example, if you're at WOT the main jet circuit is the dominant jetting circuit. It doesn't matter if you're at 10,000rpm or 3000rpm, it's the throttle position that matters. Similarly, if you're at 1/8 throttle then the pilot circuit is dominating the fuel metering--no matter what rpm you're at.

[81 clark racing]

awesome thanxs guys. you all think the 170 is to big so would this cause it to run rich? id rather hav it run rich then lean, im not fouling plugs.