ORIGINAL: rcdude7
I happen to have 65 sportster that has a ''91'' on the backplate and it came with a bag of 12'' unmarked rev-up props, I never suspected it might be a drone engine. I have not run the engine, but it looks to be a earlier K&B without the bronze bushed crankcase. I suppose this crankcas will wear its shaft bore quickly? i don't yet know what I will do with this engine but I might put it on the stand and run it some. I have some fox fuel w/20% castor oil lube.
That engine has drone written all over it. If you plan to use it in a plane, get a different carb for it. The midrange is obnoxiously rich. Fine at WOT though.
The crankcase is really high in silicon. With the proper oil and content, it should last a long time. I have 2-3 gallons through mine and there is a little play but not much. I would up the oil to 25%. Mine ran better on it. Mine won't idle for beans now though. Idle mixture is too rich in the "lean" position.