Gas Octane

[bbanna]

Just want to see if I am correct.

Was running the bike on 92 octane gas. It ran great. Did a test on milage to see how far the bike would go on a tank of gas before turning on the reserve. It went 102 miles before shutting down. So I thought about seeing how the bike ran on 87 octane.

What a mistake! About 1.5 miles from the gas station the bike ran like crap. As if the plugs were not firing. You know how it feels like when you run out of gas and the bike jerks a bit. Well under load, that is how the bike ran as if it was not firing on a few cylinders. I am going to drained he tank and only use 92 octane gas.

Anyone else have this experience?

Brian

[mrbones]

I use 87 in mine with no problem at all. That's all the stock motor needs. Unless someone changed the compression ratio in your engine (by using high compression pistons), yours should be the same, too. If not, maybe excessive carbon buildup in the intake ports and on the pistion could be causing this? I don't know..??

Or just BAD gas at that station perhaps?? Maybe it was diesel?

[bbanna]

I guess bad gas could be the culprit. A friend today suggested that as well. Does not make sense that 87 octane would make the bike run so bad. Especially since mrbones replied about using 87 octane as well with no problems.

The bike ran great all week. very crisp throttle response and all. Fill it up with 87 octane and as soon as the 92 octane is cleared from the carbs and fuel line the bike starts running like crap. Tonight I will turn off the fuel, run the carbs dry, drain the tank and put 92 back in it. Run it around and see if the symptoms are still there. It has to be the gas since that is the only thing that changed.

Brian

[ryan]

hey,
the other day I decided to try spiking my tank.

.4 gallons of 100 octane
to about 2 gallons of 91.


can't say that I noticed very much of a difference, though try to start the bike was a bitch.

think the gas was a little stale.

[Duck]

Engine is 11.5:1 compression ratio. It needs the high octane fuel. Even my old 350F speciifies 'premium' in the users manual.
-Duck

[clarkdw]

The Honda owners manual reccommends minimum 86 pump octane number (R+M)/2 or 91 RON (Research Octane Number).

In other words regular fuel. It further suggests using fuel with a maximum 10% ethanol which is what most of our ethanol enhanced fuels are today.

Honda spent a great deal of money and time designing the geometry of the combustion chamber to use the regular fuel. Using premium to increase the HP may actually do just the opposite. The burn characteristics of high and low octane fuel are different and to optimize the engine for either requires different types of combustion chamber shapes to control squish areas, swirl, etc., etc.

I spent a number of years building small Honda engines for Go Kart racing. We were not allowed to modify the combustion chambers at all. These engines were designed for low octane fuels and back to back dyno tests with regular and premium clearly proved to me that when Honda says use regular fuel you are not only wasting money using premium but you are also losing power unless you make changes to the cyl head.

The myth of using premium to gain power is just that.