RE: Too much oil.
I recently aqcuired the line of Putoline oils for glow and gas engines. Their gas engine 50-grade MHX racing oil is used by the side car MX multiple world champion. It struck me that he uses the oil in a water cooled two stroke mixed at 1:120!!! This is the only racer I know of that uses lean oil mixes. Most racing two strokes use mixes between 1:20 and 1:40
The oil is designed for 1:20 to 1:100 mixes. The manufacturer tech staff recommends to start with 1:40 though. I am running this oil in my test .15 diesel and 58cc MVVS, and in the latter now am down to 1:50. The engine inside still is very oily and slippery, like with the 1:35 I started out with. When I switched to this oil, I lost a few rpm due to the higher viscosity. Sustained power improved however very slightly.
I guess, the property of the oil to cling and stick to metal surfaces, combined with the ability to avoid metal contact between moving faces can determine how lean a mixture can be used, once sufficient oil film has been established.