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Looks like carbon build-up, LL-110 burns slower that automotive gas as aircraft engines by their nature are low rpm units, running just a little faster than a diesel does.
 

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Discussion Starter #22
Slow reviving... sounds just like a Harley
Got my rev limiter set at 5500.

but yes, Piston aircraft like Lycoming engines in PA-28, 2450 rpm take off rpm, Cruise at 1800-2000

was pitting more than build up,
I still have the old valves. Might give them a scrape to see.

Fitted bigger valves, and 1275 Hammer kit, Andrews N4 cams
 

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Yuk, always believed lead was gray, so I can't even make a guess what that might be. People tend to equate octane with "quality", and that is not it. In simple terms, octane is flash point measurement. When air is compressed, the temperature goes up. That is how a diesel works, compression raises the temperature to the point that the diesel fuel will start to burn without a needing a spark. In gasoline engines the compression is approximately 1/2 that of a diesel but the heating takes place none the less. In higher compression engines, the temperature from compression can spontaneously ignite lower octane fuel, the compression heat exceeds the flash point of the fuel. Higher octane fuel has a higher flash point so it won't start to burn spontaneously while the piston is still moving upward. Proper combustion is a flame front that moves from the spark plug across the cylinder building heat and pressure gradually (relatively speaking) With the spontaneous combustion, it explodes all at once creating almost instantaneous high pressure. That is the ping or knock sound from detonation. The reason people believe higher octane makes more power is because high compression engines of the same size as lower compression engines indeed make more power because of the hgher compression, NOT because of the higher octane fuel. Gasoline of various octane ratings contain the same amout of heat per gallon, only the flash point differs. High octane fuel in lower compression engine does not make more power. High octane fuel in an engine that doesn't need is not a "treat". If by chance the higher octane fuel contains more scavenging agents than low octane fuel, your engine might benefit from that, but again not from the extra, unneeded octane. In a normally aspirated egine, the higher your altitude above sea level, the less octane you need. The gasoline sold in Denver and other areas of similar elevation is about two octane points lower than the fuel sold closer to sea level. At higher elevation there is less air per unit volume so compression heat increase is less, your engine won't blow up on that lower octane fuel.
 

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I ran AV gas for years in all my old bikes and sometimes in my current bikes.
Had access to it through the local airport.
Now they won't sell it to you in a container unless you have a plane and then they do out of courtesy.
I just use E-free now that I can get it at the pump.
 
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