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alfa

race gas or not?

18 posts in this topic

I just got an 05 yz 450 and it says to use 95 octane or higher. Will 91 pump gas work or will there be serious problems if I don't use race gas.

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From reading other threads, Ive found out the it means 95 RON, which equates to about 91 octane US. Im trying out some 100 octane this weekend, jusr for the hell of it, and will let everyone know how I like it.

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i have run 91 pump gas to a mix of 91 and 114.i think it does better on just plain pump gas. this is on a stock o4 yzf450

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Has anyone had problems with running pump gas in a yz450.

As long as the motor has stock compression you can safely use premium pump gas. If your running a Wiseco 13.5:1 piston, then you may want to burn something with over 100 octane. Personally, I use Monster race fuel, 110 octane leaded.

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The other's were correct. The 95 Octane number in the Manual is "Research Octane". At the pump that translates to 91 octane (R+M)/2 method.

Use 91 octane at the pump, and you'll be fine. In fact these engines were designed to run on 91 octane.

In fact MXA magazine stated they got higher Horespower figures at 91 octane than from using octane higher than 96 or more.

If you go to a 13.5:1 high compression piston, than you'll need 100 octane or so. Race gas is more consistent than from the pump, but on a stock engine, I think it's a waste of money that could be spent on tires.

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In fact MXA magazine stated they got higher Horespower figures at 91 octane than from using octane higher than 96 or more.

If my memory serves me correctly (I am getting older!!) I don't believe they rejetted for the race fuel when they did the comparison. If that is the case then it would certainly explain the results.

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maybe it does have a high compression piston. I will try using race gas to see if that fixes the problem. It is the only variable I changed when I got the bike, because it does not run the way it did when I tried it.

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If my memory serves me correctly (I am getting older!!) I don't believe they rejetted for the race fuel when they did the comparison. If that is the case then it would certainly explain the results.

From what I remember, this question was posted in the "Ask the MX experts" section of MX action magazine. More than any other MX magazine, I've found them to be more Objective when doing comparison's and testing equipment.

They were the only magazine to reset the sag , raise the fork tubes, and replace the lousy front tire that came with the 2006 Yz450f, while all the other MX magazines complained about the poor handling of the Yammi. Given that, I'm pretty sure they would have compared apples to apples regarding the race fuel versus 91 pump gas.

Their recommendation was that a stock bike is designed to run on 91, and doesn't need race fuel. They stated to save the money for tires.

Now change to a 13.5:1 piston, and it's a whole new Ballgame.

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... they got higher Horespower figures at 91 octane than from using octane higher than 96 or more.
I don't want to discredit the rest of what you said here, because it's largely quite accurate. But I can produce these same results, or the exact opposite, or results that show no difference in power at all, just by selecting which fuels to test against each other.

The octane of the fuel has nothing to do with the energy available in the fuel. Nor does it have anything to do with the rate at which the fuel burns, the temperature at which it burns, the ignitability, how clean it burns, or anything else. It is true that in some cases, the methods used by fuel blenders to raise or lower the octane rating of a fuel can have a limited affect on some of these performance characteristics, but that effect cannot be judged or predicted by simply looking at the octane number. It is ONLY a measure of resistance to detonation, and that's it.

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I put a gallon or two of VP U-4 in my gas jug a couple times of year....why....cause I am a freak and I love the smell of it. Makes me feel faster. :confused::crazy::eek: Well I may be retarded but at least I am honest. :confused:

I did see a test on fuels after the Carmicheal gas debate last year. They said they got like 4 hp out of U-4. It was a pretty interesting article. The gas that is illegal for the pros to run actually tested less powerful. :lol: Does anyone else remember that article?

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I don't want to discredit the rest of what you said here, because it's largely quite accurate. But I can produce these same results, or the exact opposite, or results that show no difference in power at all, just by selecting which fuels to test against each other.

The octane of the fuel has nothing to do with the energy available in the fuel. Nor does it have anything to do with the rate at which the fuel burns, the temperature at which it burns, the ignitability, how clean it burns, or anything else. It is true that in some cases, the methods used by fuel blenders to raise or lower the octane rating of a fuel can have a limited affect on some of these performance characteristics, but that effect cannot be judged or predicted by simply looking at the octane number. It is ONLY a measure of resistance to detonation, and that's it.

Once again Gray, you've clarified info.

I guess my post was too broadbrushed. What I was basically trying to say, is that in the overall consensus, using expensive race fuel on these stock engines, will generally not yield huge gains. You're correct about the burn rate, cleanliness, and all the other attributes of fuel. I think MXA's answer was aimed at individuals who we're thinking they might have to run race fuel on their stock bike. I think it's more clear to say, that you will be perfectly fine using 91 octane pump gas for your stock bike. If you are willing to spend the extra money for more consistant fuel, that may give you some more horsepower , than run race fuel. With what looks like rising fuel costs happening again, I think the average rider would be just fine with pump gas, on a 450 that has more than enough power.

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I look at it this way. VP U4 is worth about a guaranteed 2 real hp in a bike like my '03. But so is a set of cams. The cams will cost $300 once. If I use 3 gal each ride day, that will cost me $20 extra every day I ride it. At that rate, I will have spent as much on gas as on the cams in less than 6 months, and if I want to keep the power gains, I have to keep on paying for the next 6 months, too.

I don't need the power, but some do. I don't need the additional octane, either (U4 is 92 octane, but it's Motor octane, so that's about like 96 at the pump), and neither do most others, but some do. But in deciding whether you do or don't, just be sure you are basing the decision on facts and realities.

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I tried the race gas and the problem is the same. The bike will not stay lit without using the throttle. I am going to try pulling the carb apart again, but go a little further this time. I will also try disconnecting the tps and see how it runs then. The prblem might be electrical, has anyone had problems with their CDI unit. Also, does the sparkplug have to have complete contact with the coil.

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As I understand, and someone please correct me if I'm wrong, you should match the octane to the bike. If you run too high octane, at least in other engines I am more familiar with, you run a higher risk of carbon build up as the motor is not high enough compression to burn the higher octane fuel completely. Octane is just like any other component of the bike - it's about matching correctly. If you run too low octane for your bike you run into pre-detonation. If you run too high you get carbon build up.

I think of it like this, just because you put a bigger jet in a bike (more fuel) it doesn't mean your bike will perform faster or better. Now if you add more air to match the fuel you create a better / faster motor condition (in most cases).

If you have a stock compression bike, you should usually run stock compression fuel which is 91 at the pump. This is a general rule.

However, regular pump gas may not be as clean as race fuel. Also the additive package with race gas is probably different which may or may not benefit a stock compression motor. As far as strictly octane, just match it to the compression of the motor and ride.

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