ethonal in our bikes

4 replies to this topic
  • the426master

Posted September 06, 2005 - 10:11 AM


I'm wondering my local gas station has 85% ethanol for $1.78 and premium 91 octane for $3.25 I started to wonder if the ethanol would eat the seals in my carburetor and the diaphragm in the ac. pump the guy told me the ethanol is supposed to be a higher octane than 91 and has a cleaner burn and a higher percentage of burn has any one done this or researched it.

  • grayracer513

Posted September 06, 2005 - 10:58 AM


Ethanol has been known to attack certain kinds of plastic parts in fuel systems, and its use can result in seal shrinkage, but such shrinkage is usually the result of the fact that the gasoline has swollen them to their present size. When the amount of gasoline in the mix is reduced below some point, the seals will shrink back and leak.

Ethanol, like all alcohols, does indeed have very high detonation resistance, and so has a high equivalent octane value. Unfortunately, it also has a rather low energy content, so you need to run it much richer than gasoline to get any power out of it. When used straight as a racing fuel, its biggest advantage is from the extremely high compression ratios and/or supercharger boost levels that can be run with it, rather than an increase in thermal energy in the fuel itself.

The reason it's in pump gas is to increase the amount of oxygen in the fuel in order to try to get a more thorough burn of the very lean mixtures run by modern automobiles. If you're looking for something to increase performance in your bike, I would not only look somewhere else, I'd avoid that fuel altogether.

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  • simon@vic

Posted September 06, 2005 - 12:20 PM


here in Canada you can buy 94oct pump gas from Husky or Mohawk that is 10% ethanol-blended. the Yamaha 5 valve motor seems to be okwith a 10% mix.

as for mixing your own you would need pure ethanol. mixing might not be that safe. also you don't know what other additives are in there make it all work :D

any one know if ethanol is bad for the motor?

  • Dodjy

Posted September 06, 2005 - 04:26 PM


I wouldn't touch it unless you set up the bike, specifically for alcohol. This involves making sure your fuel lines and carby seals are compatable as well as HUGE increases in jet sizes. You need almost twice the fuel to air ratio for alcohol compared to petrol. For outright power it may be an option because you can make more power by using an increased compression ratio, siko cams and spark advances etc and get cooler, more dense inlet charge but for riding in the bush you'd need a much bigger tank, and possibly a higher flow fuel system which may even require some sort of fuel pump to get enough fuel to the carby. You may not be able to get the jets. (You would also need a different type of needle and seat to control float height - alcohol carbies often use a ball and cage arangement) I think some speedway riders in OZ use the YZF motors now but I'd say they would use a different carby.

  • Matty05

Posted September 06, 2005 - 10:33 PM


It wrecks cars so why would you even think about using it in your hipo bike???
Speedway uses methanol not ethanol and you have to clean out your carb after every
meeting because it turns to jelly. My old man races formula 500's (mini sprintcars) and
they run methanol. He has to tear down the motor every few meetings too.


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