Hello Boit,

You peaked my curiousity so I called FMF myself. I spoke with Brody and asked his opinion on their choice of gas to run with a 426. He recommended, Mobil, Chevron or Amoco Premium pump gas. I then pointed out what all you said and he indicated it was all correct, for 2-strokes. He also went to add that all the Yamaha of Troy 4-strokes run pump gas.

Also, to clarify in your first post, Billy indicated that the 4-strokes were designed to run at a higher operating temp than 2-strokes.

At anyrate, I can't say enough how I appreciate your response. Guess what I'm going to do is run pump gas for a while and get a feel for it. (Because as of right now my stock bike runs with no changes runs as smooth as I could hope for.) However, you have peaked my curiousity. So I plan to also tinkering with some M2 if I can find it around here. I've never heard of it. Can you tell me who manufacturers it so I can try to find a distributor?



MR2 is made by VP. Here is a link to their site. www.vpracingfuels.com

If you want to visit another forum site with a ton of info and discussion about fuels try this, www.dirtrider.net and search the archives concerning race fuels. Rich Rohrich is very knowledgable about fuels and specifically fuels for the 426. He's the one who suggested I try the MR2 and what jetting compensation to expect.


I know for a fact that the Y.O.T. does not use pump gas. Whoever you talked to needs to get his info correct. All of the Yamaha race teams use racing fuel, including the shifter cart guys.



--Life is too short, work hard...play hard--

Sponsored by Yamaha of Cucamonga, Larry Roeseler's Stroker Fourstroke Speed Equipment and Answer Racing


The person's name was Brody at FMF racing.

Boit thanks again for all your help. FYI, I did find an outstanding article by Eric Gorr through DR. http://ericgorr.com/techarticles/Fuel_Basics.htm

It was about the most comprehensive in explaining Octane and gas in general. (Trying to see if he's finished part II.)

Anyway, you guys have given me more than enough to go on and I really appreciate it!!



Ernie: I was going to rebut the pump gas thing too, but decided to let it go. I doubt that YOT would even state publicly exactly what fuel they use and I'm pretty sure they test different fuels as well. With the 13,500 RPM redline of the 250F, I can't believe that they would use pump gas. My understanding is that they've used MR1 with excellent results.


You are right. team Yamaha uses VP race fuels.


Kfrosty; did you notice the author of that article? Rich Rohrich. I went back and read over the article again rather quickly to make sure I had not given you any bogus info earlier. Did you catch what he said about the relationship between engines with with lower redlines vs higher redlines of 10,000 RPM. He flat out states that if you aren't using the "correct" fuel for your high revving engine, you are missing the boat. I don't think he's saying that there is an explosion of horsepower to be gained with using the correct fuel, but rather that by using the proper fuel, you allow your engine to operate at its peak. The most important benefits to using the correct race fuel, in my opinion, is that the quality is consistent and jetting accordingly is fairly easy...especially with the 426. In the article, Rich describes how pump gas might be perfectly adequate as long as your engine performs well and DOES NOT suffer pre-ignition problems. If your engine performs well on pump gas and you are satisfied, I'd say "go for it".

On a persoanl note, it has been fun and another step in my educational process in jetting by using race fuel. How can you truly learn unless you are willing to try something new?

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