Which octane rating to use?

[vanram]

My 2 cents

When racing two DRZ's side by side, S-models with E-base gasket, one using Mohawk premium(with alcohol) and one using Esso/Shell premium, the one using Mohawk premium will run harder. I thought my bud did something to his bike the previous week, we are pretty competitive, but it was just the fuel. Later on that day when we used the same fuel, the bikes went back to me being able to slightly pull away because I'm a little lighter. The difference is not noticeable just taking it for a ride, but when you have something to compare to, a side by side drag race, I'll use premium fuel every time. When we went to B.C., we couldn't wait for 94 octane Chevron, the best we can get here is 92. My bike runs smoother and starts better with premium fuel. ? The competitive go carts with sealed engines and no modifications up here run Mohawk fuel premium(with alcohol) for the competitive advantage. ? Other cart racers have tried different fuel and all use that particular fuel or they will not be competitive. Am I missing something?

[dirtyjerzey]

I've been running 94 in my bike. Here in jersey we have 94 available at almost any Sunoco station.

[Tixbomber]

I noticed when I took apart my bike, a lot of carbon soot was in the cyclinder head. Would a higher gas prevent that build up? Instead of saying that a higher octane gas might not do anything for a S model with the OEM compression. Can you say that a higher octane gas would reduce the carbon buildup over a lower grade gas?

Actually, it could possibly make it worse. The misconception most people have is that higher octane means better gas. All higher octane means is it takes more heat to combust the a/f mixture. The higher the octane the higher the heat/compression it takes to fully combust. Too high, it ignites after you want it, too low and it ignites before you want it.

[slyman]

Thanks for all the responses.

I think I will run a tankfull of regular 87 octane under different riding conditions and see what happens.

Worst case is it will ping and knock a little and I will know to use mid-grade.

?

[drzrobbcanuck]

Thanks for all the responses.

I think I will run a tankfull of regular 87 octane under different riding conditions and see what happens.

Worst case is it will ping and knock a little and I will know to use mid-grade.

?

These bikes are very lean stock and will tend to ping on low octane fuel. I had to run premium until I jetted it richer. Now I run 87 (r+m/2) and have no probs on my S model. The richer jetting produces a slightly less combustible mixture which prevents detonation probs.

[Three Stooges Racing]

87 usually with the occasional tank of CAM II because it smells good.

[slyman]

87 usually with the occasional tank of CAM II because it smells good.

What's CAM II?

[Erik Marquez]

What's CAM II?

Brand of race gas.

Use what ever allows your bike to run with out pinging. Then stick to that brand, type fuel, and even that supplier if you can.

Race gas is a great thing if you have issues with quality of supplier. As Race gas is very consistent from tank to tank.. unlike the swill that comes from pumps at your local quickie mart.

[edofloat]

So all the fuel in Wisonsin is oxygenated??? That stuff turns green so fast it doesn't even need to be in the carb, it'll do it in the fuel can. To bad for you, you could always get some avgas that doesn't have any alcohol and it burns cleaner.

[Tixbomber]

Hmm... I've never had a problem running gas with ethanol. Granted that is part of the reason for the rising cost in fuel, get ready everybody else too, its coming to a gas station near you.