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blue450f

Race fuel???

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Ok..I am sure this topic has been discussed in the past, but I'm going to bring it up again so humor me. Is it worth the trouble to use race fuel in my yz450? I've heard pros and cons to using it in 4-strokes. I know the manual says pump gas is all that is required, but I always smell guys burning race gas at the tracks. Besides the fact that it smells better than bacon cooked outdoors whem camping, does it really provide that much more power? I've heard that if you do run it you need to change your jetting. Can someone educate me? Would I just be wasting my $$$$$?

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91 pump :) Unless you are racing in the pro class with a ton of motor work. U4 is good stuff but at $10 a gallon :) it takes the fun out of riding for me.

I noticed absolutely no difference from running straight VP 100 unleaded or 91 out of the pump from the same 76 station. They also sold VP 100 out of the pump for $4.50 a gallon so I tried it. Your right it does smell good though.

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u4 is good stuff but expensive and using race usually makes the bike a little fat at least it did for me

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oh and the king of race fuels is that oxengeted (spelling?) fuel that adds like 3 HP. I got 5 gallons of it for 60 bucks and boy was it worth it

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One of the current MX magazines just answered a question about this topic...

Their response was a stock YZ or WR engine runs best on 91 octane pump gas.

It's best to use 91-93 octane, if you run race gas in these stock engines you will actually lose a slight amount of power. These modern 4 strokes don't need the high octane.

Use 91-93 octane, and save your money for new tires.

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Here are some of the responses I got when I posted the same question.

http://www.thumpertalk.com/forum/showthread.php?t=265636

Ultimately I just took it back. I didn't want to start messing with the jetting and the last thing that I neede was for it to eat my graphics. The gas is expensive enough without having to throw in a set of fresh graphics every few weeks.

Good luck.

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the manual says 99 octane and above i dont see pumps with 99 octane
What manual says 99 octane? Not the one for either of my bikes. They say 92. Note that that's 92 Research Octane number (RON). U.S. gas pumps are labeled with an average of research and motor octane, which will produce a lower number. 91 Octane pump gas is all that's required, and running more octane is a waste.

VP Ultimate 4 (92 Motor Octane) is a high energy content, oxygenated fuel. Properly jetted, it will deliver as much as two hp or more in a YZ450. Is that worth $10/gallon to you? I suppose it depends....

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Here's some food for thought for those of us in Cali anyway. Any data about pump gas and octane needs to be understood that it assumes GASOLINE. At one point recently I saw info indicating that pump "Gasoline" in California was actually 90% MTBE. It was one of the dirty little secrets of the Clinton/Gore years, sounded great until they realized it's seeping out of tanks and polluting the water table. There are lot's of different formulations of "Race Gas", and some of it makes a big difference in power in the right circumstances.

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Well

I just picked up a new 5 gal jug of U4 as it is now called - not Ultimate 4 anymore - and on the can VP has added a sticker " Drain carb after each use" ...... I have been saying this since it came out and it finally got placed on the Blue can....

and yes it is worth every dime.......to me..... :)

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Any data about pump gas and octane needs to be understood that it assumes GASOLINE. At one point recently I saw info indicating that pump "Gasoline" in California was actually 90% MTBE. It was one of the dirty little secrets of the Clinton/Gore years, sounded great until they realized it's seeping out of tanks and polluting the water table. There are lot's of different formulations of "Race Gas", and some of it makes a big difference in power in the right circumstances.
I think you'd better re-examine the info you're remembering. I don't think that CA fuel was ever any more than 10% MTBE. More than that would require re-jetting the car to drive out of state. (It's a form of alcohol)

MTBE doesn't seep out of tanks. It is so water soluble that its airborne vapors, whether virgin or as unburned residue, either settle to the ground, or wash out of the air in rain. Whereas petroleum pollution of ground water will separate and be filtered by the soil itself, MTBE blends with water, and stays in it. Now our wise state leaders are trying to get the oil companies to clean up the mess that they ordered the oil companies to make, even as they persist in mandating MTBE be used in fuel. And for those of you who like to use gasoline as a cleaning solvent, MTBE is very readily absorbed into the skin, and is a dangerous cumulative toxin.

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I think you'd better re-examine the info you're remembering. I don't think that CA fuel was ever any more than 10% MTBE. More than that would require re-jetting the car to drive out of state. (It's a form of alcohol)

MTBE doesn't seep out of tanks. It is so water soluble that its airborne vapors, whether virgin or as unburned residue, either settle to the ground, or wash out of the air in rain. Whereas petroleum pollution of ground water will separate and be filtered by the soil itself, MTBE blends with water, and stays in it. Now our wise state leaders are trying to get the oil companies to clean up the mess that they ordered the oil companies to make, even as they persist in mandating MTBE be used in fuel. And for those of you who like to use gasoline as a cleaning solvent, MTBE is very readily absorbed into the skin, and is a dangerous cumulative toxin.

You may be right about percentages, but there's plenty of info online (including a report to congress) about MTBE (and gasoline in general) leakage from underground tanks. The point is there's more BTU per gallon of gasoline without MTBE than with it.

That means more power.

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You're right about the BTU numbers, and that's a good example of how "oxygenated" doesn't necessarily equate to higher energy content.

In California, underground storage has become something of a paranoia with the State, and tanks are regularly inspected. Any of them that fail a pressure test are pumped out, dug up, the soil around it removed, and the tank replaced, at the station owner's expense. Another reason theoil companies own so many of them nowadays.

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I know out here on the east coast, they Oxygenate the fuel, and my truck definately performs worse with this type of fuel. I lose about 1 MPG, and the truck feels sluggish. I have had professional mechanics tell me it's a joke because it causes modern cars (with computer controlled fuel injection) to simply richen the mixture, thus eating more fuel.

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Okay back to the subject.... :)

I use Citgo 110 leaded race fuel. I love it, it adds a noticable snap to the bottom end and feels like its pulling harder all the way to the rev-limiter.

And it also smells good!! :)

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Okay back to the subject.... :)

I use Citgo 110 leaded race fuel. I love it, it adds a noticable snap to the bottom end and feels like its pulling harder all the way to the rev-limiter.

And it also smells good!! :)

becareful with this gas - it has been known to eat away the seals in carbs as most high octane race fuels have....

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