what gas to use on older engines

[Jerry Wieland]

Cory Your panhead is totally capable of being rebuilt with quality parts that easily withstand the stress of todays' fuel. I had over 100,000 miles on my 46 when I pulled the motor and it still had a lot left. I pulled it because it was in a 1941 chassis and I got my 41 FL engine together - just in time to run it in 1000 miles and then head out as support pulling a sidecar on the 2010 Cannonball Run for 4200 miles. We hit 100+ degree weather in Alabama. When it was over Amklyde and I left Santa Monica and headed 300 miles north to Modesto. The temperature was 100+ and we were traveling at freeway speeds both pulling sidecars. If we were going to have trouble that is when it would have happened and both bikes never missed a beat.

Jerry

[Grizz]

I have said it before and old timers laugh at me. I run 100 octane low lead aviation fuel in all my cycles and lawn equipment also Generators, at least 50 percent mixed with pump gas when possible. Not so much because I need octane, but it has every thing you need. And talk about smell good. If you want to go fast racing fuel can be had in several high octane but cost way more. If I can't find AV gas on a trip I will buy it. You won't need to scrape carbon or buy gaskets any more.
I buy aviation her at a small air port with no gate and get it any time I am in the area, either right in what I am or in container to keep at the shop.
If you run it all the time and you are not passing oil the in side of your pipes and combustion chamber will be grey. When I do pull my ported and polished Shovel Heads I wipe them with a rag and they look polished again.
You won't need sablizer any more, I do use seafoam any time I drag home an old bike that I want to start to help clean carbon out.
Jim Rowin

I agree 100% with Jim, Avgas does not jell, it leaves a blue green film in float bowl and as soon as you turn on the fuel it just dissolves. Iv'e had it in bikes for 10 years and bike starts like it was last run yesterday... Phil

[harley1]

I also ran avgas in a couple of 70's HD's with no problems. The avgas seemed to keep the inside of the motors and exhuast clean. Smelled good too.

[camsaure]

I am a fan of 100LL avgas. Works great in Shovelheads and the higher compression Pans. 100LL is real gas with real tetraethyl lead in it. Try this expirement: pour a little car gas on your sidewalk or driveway and next to it a little puddle of avgas. The avgas will evaporate completely leaving only a small trace of the blue dye it contains. The car gas will leave a greasy spot behind. (you can clean the greasy spot afterwards with a little avgas). Avgas has an actual octane rating around 105, that is too high for flatties and other lower compression engines. It could be mixed with other gas to lower it's octane or other remedies. But in lower compression engines I believe the benefit to be the lead that it contains. If anyone is anal about EPA I should mention that it is not legal to use any dyed fuel in any highway use. The good thing about real lead is for protecting and lubing the valve seats. Valves are easy to replace, not so much with the valve seats as anyone with old pan heads or flattie cylinders can attest.
Avgas has also worked well for me in chainsaws ,weedwackers,etc that sit for a while and always seem to need their carbs cleaned in order to get them running again.
My experience with 100LL started with airplanes. I hated to work on airplanes where the owners tried to cut costs by using car gas instead of avgas. (100LL is too high octane for many aircraft engines, especially the older antiques and classics) Aircraft that had run car gas that sat for more then a month always had a stinky, greasy mess in the carb, making them run crappy. So much for saving money! There was also a greasy mess in the fabric around fuel tanks that would bleed through the dope when attempting to rejuvanate old dope on the fabric. What a mess! 100LL is to high a rating for many antique engines. I have a 1929 Great Lakes biplane with a 125 hp Menasco engine in it. The Menasco could run on 68 octane. I chose 100LL due to the greasy residue from car gas, but have to take precautions(once in a while I can find 80 octane avgas though) I like many other antiquers use Marvel Mystery oil and another lead dispersing additive. The excessive lead in avgas tends to cause sticky valves, hence the need for a couple of additives. This actually works much better then car gas, even at that high of octane of 100.
Lycoming actually had a service bulletin out several years ago. It was about valve seat problems in engines that use car fuels. It was to the effect that if you intended to use automotive fuels you should at least run a tankfull of 100LL through the engine after any valve work has been performed, in order to coat the seats. They claimed that this would last quite a while in protecting the seats from wear. It sure couldn't hurt to use a little in MC engines after valve work to be safe. These are just my opinions that have worked well for me, and everyone is free to come to their own conclusions. Merry Christmas!