Race Gas or Super

Are there any benefits to running race gas in the 400/426? Is a mixture of the two better than plain Super or plain Race gas? Trick is geographically very accessible to me and wonder if I should run it in my 426.

As far as I know it depends on how your jetting is. I run super on my bike but every once in a while I do mix a little bit of CAM 2in the tank. It isn't as important if you are woods riding but will definately give a little boost if you jet your bike to handle it.

I run a mix of Torco 110 race gas and Amaco Ultimate 93 for an aproximate 98 Octane rating. The 426/400 will run on high quality pump gas. Running a blend allows for a more consistant preformance over a broader range of conditions it seems to me. Race gas is formulated for spefic engine demands, so be careful what kind of race fuel you go pouring into your scoot.. It may actually harm performance more than help.


HomePage www.eagle-racing.com

After finally getting my jetting down to where it runs good and the plug looks decent (3000' ele, 168 main, next leaner needle (middle clip) fuel screw 2 1/4 turns out) I tried a mix of 2 gallons 92 Oct and 1 gal of VP 110. It killed my mid-range and the plug was white. Drained it out and went back to straight 92 Octane, no problem.

I have always run straight race gas in all of my bikes. In an effort to save $$$ since race fuel is expensive I suggest you mix at least 25% leaded race gas. The lead helps to lubricate the valve train and will enhance performance by allowing the engine to run a bit cooler. When Larry Roeseler speaks I listen!!!


The race gas is not as lubed. as pump. This might sound weird but p/g has more oil in it and keeps it lub. better...There has ben 5 people from shops out of my area tell me that. I run straight prem. I will run a small amount of good stuff somtimes. I think its a wast of$$$$$ for me.


According to MXA you're NOT supposed to run race gas in a 426. 93 octane pump gas is good. This came up last year and I can't remember the details but someone here came up with a good link that explained how 93 pump gas is actually 95, depending on your state. I'll look on my other machine and see if I can find those links...

My 400 and 426 are able to run on premium unleaded fuel. My concern is is this...pump gas is designed to perform on lower compression engines and not a 12.5 to 1 compression ratio. I am also concerned with the consistancy of pump gas. The octane rating for pump gas can vary as much as 2-4 points. You may think you are getting 92 octain fuel but in actuality you may be getting 89 octane.

My experience with using race gas has been good and I have not experienced any of the problems that the magazines have mentioned. When I first got my 98 400, I spoke to Larry Roeseler about the fuel issues and he was very clear in describing the octane and leaded fuel needs of a high compression engine. Jetting changes may be necessary too.

When $$$$ are short I will mix 50/50 but I will never use straight pump gas in my bikes.

I guess I am lucky to have a mentor like Larry Roeseler to guide me.


There are really only two needs/benefits to running race gas (higher octane). One is the higher the octane, the cooler your cyliner temps are. Two, prevents detonation with higher compression engines. If your bike is not running too hot or you're not experiencing detonation with premium pump gas, you don't need race gas! Don't waste your money!


Try this one and look under FUEL FOR THOUGHT.

very interesting!!!!



That's not thunder ridin' your BUTT .........

It's a whole Damn HURRICANE!!!!!!

Rich Rohrich has a forum at www.dirtrider.net that is a wealth of information about fuels. While there are many variables to consider when selecting a fuel for your bike, what is pertinent for the 426 is the RPM redline and compression ratio. Good quality FRESH pump gas would probably run just fine in this bike, however, typical pump gas is FAR from being consistent in quality. A fuel such as VP C-12 is an excellent match for this engine design. Keep in mind that this engine doesn't hit the rev limiter until 13,200 RPM! The lead content also cushions the valve-to-seat contact.

You have to keep things separated.

The most usual race gas is made out of acetylate.

This is a strickly chemical mixture that contains approx. 08-1,2 % Oxygene.

This is cleaner and containd clean chemical additives that will keep Your valves, piston a.s.o lubed allright.

The only thing is: If You run it at a low comp. ratio, it will give You one effect only: The price and nothing else.

In a high comp. engine it will give You a better mid range punch and a smother powerband. One throwback is that it will be more sensetive of jetting.

Hope this helps!! Numpsy

you guys are so far out in left field that it is funny. only Boit is on the money and he has the redline of the 426 all wrong (11,200 not 13,200). the 250F i ride is 13,500.

MOST race gas is not even designed for 13,000 rpm. i talked at length with a Howell Fuel distrubitor and he said they had NOTHING to offer me. my motor spins way to FAST for their race gas. now, think how bad pump fuel must be. he said their best stuff that is designed for 9800rpm is no good.

now, i live relatively close to the VP world wide distillery plant. i KNOW of 2 guys that actually work at VP. one of them was in my class the last 2 years. i was in the first VP GP race on the new VP MX track there in Floresville,TX.

in order of best fuels to run for a 426 or 250F:

VP Red, VP103, C-12, C-14 and C-18.

that is for NON-oxygenated fuels with C-18 being the best. MR2, MR3 and MR4 certainly have their place, but are VERY expensive to run. all are 2.55% oxygenated. MR2 is the fuel that all of the SuperCross and MotoCross pro's run.

MikeOK, dude, lay off the crack pipe. race gas is NOT gonna hurt that carb. i know several guys that have run NOTHING BUT race gas in their '98yz400's since day one. they still run fine. my 250F has had race gas in the tank since the day i first fired it up.

what most of you are failing to understand is that the 250F/400/426 motors are RACING engines. they are not designed for taking grandma to the corner for a loaf of bread and a quart of milk. the factory specified IDLE of the 250F is 1700-1900 rpm. that is IDLE!!! how many of you notice the rpm of your car/truck cruising down the hiway at 65mph? yeah, now realize that these race bikes idle at almost that rpm. grab a clue!

[This message has been edited by SUnruh (edited 03-08-2001).]

Originally posted by SUnruh:

…think how bad pump fuel must be.

So bad that it is recommended in the manual, while race gas is not. According to Yamaha, (the company that manufactured the bike) the YZF is designed to run on premium unleaded. They obviously need to grab a clue!

They are not designed for taking grandma to the corner for a loaf of bread and a quart of milk.

That may be true, but don’t tell my grandma. :)

Yamaha does say in the manual that pump gas is ok...95 octain pump gas. I have not seen premium unleaded above 92 octain in southern California.

How many bikes would Yamaha sell if they told you that you have to run race gas for the bike to perform properly? Probably not to many. That is also why the two strokes are jetted fat from the factory so you don't go out and sieze it right away.

I have run only race gas in my 400 and my 01 426 since they were new. I have NEVER had a problem with the carbs becoming gumed up. I have over three years of riding, practice and racing on my 98 400 and my carb has never been apart except for jetting changes.

Larry Roeseler tells me that I would have never got that much longevity out of my 400 without using race gas. This is because of the consistancy of the fuel quality and the higher octain. He said even though you may not hear it detonate on pump gas, the running temperature is substantially higher. Higher temps result in faster oil breakdown, increased heat related issues within the engine and the list goes on.

I know race gas is expensive but you get what you pay for.


Yep...was wrong on the RPM redline. I knew better but must have had a brain burp. I had a car accident a few years ago and suffered dain bramage. That's my excuse and I'm sticking to it.

Haven't you guys figured it out yet. I'm hearing alot of you saying "there's only 92 octane gas around here". Well, your right.

It's economics, pure and simple. The Yamaha manual says to use 95. Oh, I can't buy it but I can buy the Yamaha "octane booster" and put more money in the company coffers. It's the same as the oil. Yamaha does not have an oil well in some secret location pumping out oil that will only work in there engines.

If they can keep you confused just long enough for you to buy their overpriced "yamalube" products, cha-ching........$$$$$$$.

Octane ratings of pump gas in the US use an average of two methods, RON and MON. Look at the yellow octane sticker on the pump, underneath the rating it says (RON+MON)/2. I think one is Research, the other is Measured Octane Number.

I forget which, but one is generally higher than the other. The point is that an avg. of 92 should be equivalent to the recommended 95. Actually, the REAL point is that if the motor ain’t knockin’ then higher octane is not warranted. Lots of factors affect how much octane a motor needs so individual experience matters more than what is recommended. YZFs at sea level may well suffer preignition on premium unleaded in certain conditions, but here in the high dez my 13.5:1 YZF does not.

I’m sure my bike would run better and last longer (unless the tranny goes again, will race gas prevent that?) on race gas, so it is probably better than spending money on carbon fiber and Ti, but it ain’t gonna win any races for you.

My bike is plenty fast on pump gas, thank you, and I have no reasonably convenient or reliable access to the proper race gas anyway. Running the wrong race gas may actually cost HP vs. pump gas. It sounds like SUnruh knows what is what so if you want race gas buy the stuff he recommends.

I did not know that Yamaha made octane booster and I did not see where the manual recommended it (like it does the Yamalube engine oil, Yamabond etc.), otherwise I might agree with you Mojo. What I don’t get is why they say that race gas will ruin the carb, obviously that is not true, hell I bet their race bikes all use it.


Actually Yamaha does make the Octane boost. I read the maunual and it didn't recommend the boost..but...if all that people are seeing is 92 as a high, they'll call their dealer and he could help out with an overpriced additive. Your right, it didn't say to use their product in the manual.

I concur with you wholeheartedly on the fact the bike is plenty fast on good old super at the pump.


Thank you Hick! I don't think I could have said it better!

[This message has been edited by dirtdad (edited 03-09-2001).]

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