Octane question

[Davey Do]

The instruction manual I got with my 49cc four stroke HuaSheng engine recommends 93 octane gas. I first ran my motorized bike on 87 octane that I had for my mowers and the bike did well. It pulled a relatively steep hill with no pedal assist and I was impressed. I thought performance would improve with the 93 octane gas, but if anything, it's decreased.

Now, I've been playing around a lot with the drivetrain and wheel adjustments, so that could be a reason for its decreased performance.

As a side note, I run my '51 Chevy with its '57 235 straight six on 93 octane and it does better than with 87 octane. A carb expert told me that those old carbs run better on lower octane, but I've found the opposite to be true.

I'm going to try the 87 octane again as an empirical endeavor, but in the meantime, I was wondering what you all thought.

 

[Old Busted Hotness]

Higher octane just reduces pinging because it burns slower. These engines don't have enough compression (7:1) to ping, unless they're overheated or way over-geared. I've only ever run 87 and never heard a ping.

 

[Chainlube]

I run premium fuel because I don't ride every day. We don't have any alcohol in our premium so it doesn't go stale. If you use regular grade, use 2t oil with a stabilizer in it.

 

[darwin]

No ethanol in premium fuel? I need to check that out here in CO, never really looked. I usually run midgrade here in my m/c. It does have the ethanol in it and Yamaha recommends it.

 

[Wrench]

High octane fuel 91 or 93 is for high compression engines to prevent preignition - ignition before spark


High octane 91 or 93 fuel is used in 2 stokes Because adding oil to the gas dilutes the gas lowering the octane rating to 89 or 87

 

[Chainlube]

No ethanol in premium fuel? I need to check that out here in CO, never really looked. I usually run midgrade here in my m/c. It does have the ethanol in it and Yamaha recommends it.

I live in western Canada and it's all ethanol free premium up here. I've heard a few of my cart friends from the US complain about ethanol.
With a 40 oz whiskey bottle and a half cup of water you can remove the ethanol from the fuel you buy. Put the water in the bottle, mark the level of the water and then top up with fuel. Shake the bottle for a while and then mark your water level and see how much it rose. Ethanol likes to bond with water better than it likes gas.

 

[Chop-chop]

Toluene, a commonly available solvent used to make gelcoat is what petrol companies add to petrol to increase the octane rating of the fuel. There is a formula that is used to calculate how much toluene by volume is needed to add to the petrol to increase the octane rating by a certain number of points.... I think it's 15% toluene by volume increases the octane rating by 3 points.... I used to make my own high-octane blend for my big horsepower Skyline this way before I switched to running Methanol....

 

[Chop-chop]

Now I run a blend of 60% methanol to 40% unleaded petrol. This 60:40 blend has an octane rating of around 104 or 106.... which is perfect for my car running 2 bar of turbo boost... I now wonder how this blend would go like in a 2 stroke bike engine lol

 

[Street Ryderz]

Now I run a blend of 60% methanol to 40% unleaded petrol. This 60:40 blend has an octane rating of around 104 or 106.... which is perfect for my car running 2 bar of turbo boost... I now wonder how this blend would go like in a 2 stroke bike engine lol

waisted time and money our 2 strokes don't have high enough compression to require high octane and it actually hurts the performance.

 

[darwin]

Just ride down to the station and filler up. Put your efforts into riding, nuff said!