ORIGINAL: GallopingGhostler
ORIGINAL: flyinwalenda I think this engine with the stout 20:1 mix will act like a glow engine with similar amounts of exhaust residue albeit less than the initial break-in cycle. I doubt it will run as clean as the typical larger gasser engines.
Found the reason for the 1:20 oil/gas ratio on Page 10 of the manual:
The bronze bearing at the bottom end of the conrod depends upon this lube ratio to operate properly. Personally I can live with that. I can also see this engine in applications for vintage control line aircraft. The $3/gallon (NM) versus $25/gallon glow certainly has merits.
They hadn't updated the instruction manual for the engine at its time of release, but there is a needle bearing on the big end of the rod now. For production they had the needle bearing put in. The earlier prototype engines had a bushing on the rod though.
The problem is no one really knows what using a reduced oil ratio would do to the engine if anything. So they are being conservative on the suggested fuel/oil ratio needed with the engine. It may very well work with less oil in the fuel, but no one really knows for sure yet. One issue is as the engine gets smaller and smaller it needs more and more oil in the fuel to stay properly lubricated.
I would suggest using the factory suggested oil ratios for now. After breaking in the engine really good, then after you have a extra set of parts on hand for rebuilding the engine, you can try running less oil in the fuel and see how well it holds up. I can see going from 20:1 ratio down to a 25:1, but it is iffy if a 32:1 ratio would work Ok or not. I just would not try it unless I had spare parts on hand. But as many more people get the engines and use them, we will start to see some trends develop. Using a high quality synthetic oil may let you reduce the oil ratio needed versus using low grade mineral oil stuff.
if ylou think about it, we really haven't had any small production gasoline engines made and being used since before World War II. There aren't a lot of people left from that time era either. So we are sort of having to re-invent the whole thing nowadays. also way back then the quality of the oils wasn't very good and we have much better oils available to us today. They used to use SAE 70 and 80 weight mineral oils in the old days. we now have some really good synthetic oils available to us today. Plus the modern engine designs are much more modern with ABC cylinder pistons, better metalurgy, higher precision machining, ball bearings and needle bearings, electronic ignition and so on.
I would suggest using a really high quality synthetic oil in the engines so as to reduce the carbon buildup that occurs using mineral oils. Since the engine is smaller, the carbon buildup will be more pronounced in it as compared to a larger engine. The little spark plug could foul out a little faster with lower grade oils.