i have a 04 yfz 450 with intake and exhasut and cdi i was told i need to run race gas in my bike is this true any help is appreicated?

If the cdi has advanced timing, I'd say yes. Call the manufacturer of the cdi and ask their recomendation.

Assuming the bike has stock compression you shouldn't have to run race fuel BUT, YFZ's have high compression as far pump gas is concerned. If the CDI advances the spark timing greatly you may be close to detonation. I doubt you need to run straight race fuel either way, maybe a 50/50 blend of race fuel and 91 pump at most to be safe.

Unless you have had a custom CDI mapping done, no aftermarket CDI will advance the timing that far. The stock Dynatech curves are not that aggressive. YOu can program it to be, but stock they are not.

Lets get this straight race gas / higher octane fuels prevent detonation. Unless your timing is advanced and/or high compression, there is no reason to run race gas. You can run race gas in a stock motor and it WILL NOT give you more power, PERIOD!

ok rant off.

I am curious as to who told you you must run race gas? Again, you should not have to run race gas.

in my amateur opinion mine runs better on a 50/50 mix of U4 (95 octance?)and 91 than it does on anything else--straight U4, Straight or mixed F&L (111), straight or mixed VP(c12)

Not faster, but it runs clean and crisp and a little cooler (fan does not come on as much)

I have had zero problems

Dr. D slip on, jetted, K&N filter

50/50 would be wise....


Correct me if I'm wrong but isn't 160lbs of compression the limit for pump gas? Perhaps it would be good to run a compression check.

Your right, it may run cleaner. I was refering to those who think they are faster with race gas!

Why? He has no reason to run race gas! a pipe, intake, cdi? Most CDI's only raise the rev limiter by 750-1000rpms. Nothing else. Dynatech and vortex are the only ones that do more.....

Personal opinion. Not because it'll make it faster, just as you mentioned before, higher octane fuel is more stable under more radical conditions.

I don't know much about the CDI, but as mentioned before, if it tweaks the timing, it wouldn't be a bad idea.

Thats cool.

the guy i bought it off of said big gun said to run race gas in it 105+ octane in it big gun is the one who sety the motor up sooo.... thats why i ask cuz i know race gas wont give you any power you just need it for hc or adavced timing by alot.... so thats why i asked

well, be carefull. I would call the guy up and find out EXACTLY what was done! Who knows what a "set up" motor is to Big Gun. It could very well have a High Comp piston in it!

I would check!

As stated, you only need to run high octane race fuel if the compression has been raised. That could be done with head work or a high compression piston or several other options. You need to find out exactly what was done to the motor. If it is just a stock yfz motor, your fine with 91 octane.

i found out last night everyhting is stock internals just bolt on setup by big gun i saw the reciept on what they did and the guy said the cdi bumped up the timning and that is why he ran 105 octane gas

DO you know exactly what CDI it is?

no i dont know but when i pick up the bike i wilol know for sure i am also getting the stock one with it tooo

race gas is a waste unless you hit the interl components of the engine. 91 in my bike, purr's like a kitten. and roar's like a lion! race gas for race bike/cars.... as far as the timing issue goes with the CDI, you can only go so far. personally, aftermarket CDI'S are worthless unless for specific motor build. if you think about it, you dont lift the rev limiter on a stock engine, even with intake and exhaust, your not going to make more power. just going to break stuff. a bike is no different then any other machine. Your quad isnt your tool to make money, its to enjoy. no one enjoys broken stuff. put the stock CDI on and run 91. IMO