Best octane gas?

[sarah1]

hey southernman youll be getting the 100 LL and i found that some airports wont sell it to you if you put it directly in your bike
.I have had to go there with 5 gal cans and tell them it was for a home built when and if i was asked.

[pops]

Even though it's called LL (low lead,) avgas still contains much more lead than auto gas did. Runs great, but the lead is very corrosive stuff. That won't be a big problem if you run without mufflers but you will still have to consider trade offs with the headpipes and valves. It's no coincidence that Midas started dealing in brakes and shocks since lead was removed from gasoline. When's the last time you or any of your friends had to have a muffler replaced on your car? They used to last 2 or 3 years at best before rotting out. Now they don't rot out.

pops

and the dealer who sells you aircraft gas can get into big trouble for doing so

[pamcopete]

pops,

If the buyer declares that the gas is for use in an aircraft, then the seller is off the hook.

[srust58]

I was always under the impression that high octane gas was for higher compression engines. 93 is harder to ignite than 87 so you don't get pre-ignition from compression with the higher compression ratios. Run low octane in a high compression engine and you may get pre-ignition. Run high octane in a lower compression engine not designed for it and it will not burn completely leaving carbon deposits. Do it long enough and you create an octane junkie, the heated up carbon deposits can cause pre-ignition if you then switch back to lower octane gas. I have run regular gas in my 79 for 30 years with no problems. For my Honda CB750 Super Sport I run a higher octane as the engine has a higher compression that the standard CB750. Although I have run regular in it with no problems at times.

[rikroc]

I pulled my carbs apart and the pilot jet plugs had turned to goo. Is ethanol to blame? Or aftermarket rubber?

[tomterrific]

Just run the highest octane at the pump. It is a falicy that it ignites harder or burns slower. You can never tell when the planets will align and the piston will hole.

The lastest victim: I ran into a young fellow at VMD who just built his first bike, Honda CL350 Cafe. This guy has been showing up at VinMoto night for a few weeks happy as a $1000 a night chippy with the bike running fine. He had a sign on it at VMD, "Need Engine". I asked if he holed a piston on the way up and he said he had. I asked if he had 87 octane in the tank and yes he did. This guy would not have had a problem if he was running higher octane.

Tom Graham

[orforester]

I didn't hear about the addition of Sea Foam and the benefits of it, vs. no additive? In Oregon, our Govenor believes in helping the economy by putting ethanol in all gas, so we can't buy anything that does not have it. I junked two Lawn mowers already, and my mileage in my pickup lost 20% MPG, I really wonder where his head was at, or how much research was done prior to that decision. But tell me about Sea Foam, I bought a bike from a guy who gave me a can and swore by the results of it, I didn't see any difference

[rossco59]

I run Shell V-Max 98%. I can really notice the difference in power but cold starts require max choke and a good warm up. Am I at risk using this fuel.

[jscribner]

I run 93 octane whenever it's available. And (and I know this might be witchcraft) I add a little Lucas Oil Cylinder Top End Lubricant to each tankful. A bottle (about $10.00) lasts me almost a year and a half of riding. My bike seems to like it, though I also think it makes me run a bit rich.
John Scribner

[blbrodie]

Sometimes when I decelerate quickly, there will be some backfiring. This is not the same as pinging, correct?

[xulf13]

no, it is not the same as pinging. Thta is cause by air leaks in your intake or carbs or running lean. if it's coming out of one exhaust only, then it is very likel you have an air leak. When you descelerate your throttle plate close and wherever the leak is will continue to flow air to the very little amount of fuel left int the throttle, causing a backfire.

[xsleo]

When these bikes were built most regular gas was 94 octane. High test was 104 octane.
They built the bikes to run on the gas that was available at the time. So if the bike was built around 94 octane why run 87 ?

[ShakerNorm]

I usually run regular in my '79 with no problem - until I got stuck and had to run E85 - and my bike ran like CRAP! Luckily it was only for one tankful, then it was back to normal again. Also luckily, it didn't have enough time to eat away any of the rubber parts, either.....

The rubber parts in the fuel system of these old things were never designed for Ethanol - and they can deteriorate pretty badly when you use it. Lucky for us - there are a few outfits out there who make parts that are compatible with the ethanol (and Mike's is NOT one of them.....).

[xsleo]

I got an 81 Special a couple weeks ago. As i was chec king things out I found the answer to the question that started this thread.
The left side cover over the air cleaner boxes has a Vehicle Emmission Control Information sticker on the inside.
It tells a few things about the bike. Idle speed-1200 rpm. Timing 15* btdc. Gasoline grade Regular Research Octane: 91 min.
Most gas stations don't have 91, the sticker says 91 min so 93 is the only thing above 91. Unless your station has 92.
I think that should pretty well answer the gas requirement question.

[pamcopete]

xsleo,

As previously posted in this thread:

To determine your vehicle's octane requirement, look at the manufacturer's recommendation in your owner's manual. Most auto manufacturers recommend 87 octane gasoline, as measured by the (R + M) / 2 method on a test engine under defined operating conditions. If the vehicle knocks on the recommended grade, a higher octane grade should be selected.

Some foreign vehicle manuals recommend a Research Octane Number (RON) instead of the more common octane rating that appears on most gasoline pumps. As a rule, the recommended octane rating can be determined by subtracting four (4) from the recommended RON number. A vehicle that calls for "91 RON" could use 87 octane gasoline (as measured by the (R + M) / 2 method).

The placard on my '81/H says "Research Octane 91 min", which translates to 87 octane minimum at the pump.

The (R+M)/2 is the standard displayed on the pumps.