race gas ?

In the past I have always used race gas in my yz250 and it held up well. Now I have aN 03 WR450 should I still us it or would highest octane from the gas station be ok? I would like to hear everyones opinion on the matter.

I run 91 octane in my WR420, which is supposed to only run on 110. It seems to run good.

The highest available pump gas octane is fine. I use 93 here and no detonation at all.

I have always tried to use the highest grade pump gas in my WR. There have been several occasions where the only choice was the lowest grade pump gas or no riding that day. Needless to say the lowest grade pump gas was used and the bike ran fine. Solid machines.

My 2002 426 needs at least 95 average (R+M/2) octane to run strong without pinging. I mix 1/3 100LL Av gas with 2/3 91 pump gas.

Some Union 76 stations in California offer 100 octane unleaded gas. the manual warns against using leaded fuel. My '03 runs without pinging on 91. I have heard that using high octane at high altitudes can help avoid re-jetting!?!?!?

There are other threads on race gas with more complete info. Here's the readers' digest version:

The only thing that requires more octane is higher compression. If your engine is stock, you don't need race gas anywhere. 91 pump gas is fine. You can run it if you want, but you'll spend more money for no/nada/zero gain in performance. You will also likely have to rejet to switch to 100 octane.

Anyone tells you they got a performance gain by simply switching to race gas has one of three things going on: Either (1)they have a modified engine with high compression, or (2) their jetting was already wrong for 91 but right for race gas, or (3) they're dreaming. Or more than one of the above.

Very, very few people actually need race gas.

That would explain why I never had to re-jet my yz250 (jetted at sea level) I brought it to Co. from CAli. and rode it from 8000' to 12000' and never had a problem.

I believe WR and YZ both have high compression motors :)

It is not only a question of compression, but, also engine timing.

1. It is true that you can get more performance out of a high compression engine (like our yamahas) using race gas (100 octane) if you increase the timing and lean the carb. But, this is a lot of work on the dyno and you have to change the spark timing.

2. The bikes from the factory are setup for premium gas. this is what you should use.

3. Remember, race gas is harder to ignite and has less explosive energy than premium, so, unless you do number 1 above, your bike will be slower. I know this, because I used to drag race cars. Everytime, I used race gas without changing my tune, the car was slower in the quarter mile. I could get my car going faster with race gas (100 octane unleaded) only after I increased the timing and leaned the fuel. This is possible with race gas since it has a higher threshold for pre-ignition or pinging.

For our Yamahas, believe me, race gas is not worth the effort. Also, the higher altitude your ride, the less octane is required for a motor. So, if you are constantly riding at 6000 feet or above, you can run 89 octane with no pinging and you might get better performance out of your bike.

Personally, on my WR426F, I tuned it with 91 octane at 2000 feet and always run that no matter where I go. :)

A buddy had a 302 motor built for his CRF250 by RPM. They told him 93 octane for outdoor type tracks and 91 for supercross style tracks. They said the bike would pull harder out of corners with the 91.

Leaded Gas + Hard Valve Seets = Big No No

Leaded Gas + Hard Valve Seets = Big No No

Care to share the logic behind that statement?

Valve seats are actually hardened to withstand the lack of protection that is provided by TEL (tetraethyl lead) used in leaded gas.

We are still stuck with lousy MMT rich gas in Canada. USA's RFG (reformulated gas) sounds pretty good...

I use Citgo 110 leaded fuel in my 426, I have for over 2 years with no problems.

Heres my reasoning for using the race fuel: Race fuel is pure, it is always the same everytime I buy it, pump gas is not. You can jet a bike with leaded fuel 10 times easier than a pump gas bike, because leaded fuels don't leave black carbon crap from the additives they use to water down the pump gas. Leaded fuels keep the engine very clean inside, when I replaced the top end in mine this winter it was so clean that a shop rag sprayed with carb cleaner removed all the debris from the valves and the top of the piston. More power with a quicker response, I don't have a dyno, but I can feel the difference in the off idle snap my bike has with the leaded fuel.

I would recommend using race fuel in all the Yamaha 4 strokes. My fiancee has a YZ250F and the leaded fuels benefit that bike aswell. :)

I use Citgo 110 leaded fuel in my 426, I have for over 2 years with no problems.

Heres my reasoning for using the race fuel: Race fuel is pure, it is always the same everytime I buy it, pump gas is not. You can jet a bike with leaded fuel 10 times easier than a pump gas bike, because leaded fuels don't leave black carbon crap from the additives they use to water down the pump gas. Leaded fuels keep the engine very clean inside, when I replaced the top end in mine this winter it was so clean that a shop rag sprayed with carb cleaner removed all the debris from the valves and the top of the piston. More power with a quicker response, I don't have a dyno, but I can feel the difference in the off idle snap my bike has with the leaded fuel.

I would recommend using race fuel in all the Yamaha 4 strokes. My fiancee has a YZ250F and the leaded fuels benefit that bike aswell. :)

leaded fuels :D:):D:worthy::D

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