Oldmaddog,
I have always been careful not to overfill the oil. I changed it at 3000 mi. to Honda HP4M (10w-40). Engine was quieter, but still have the noise when the engine is hot. Does shift better. Almost have 6000 on it now, and I am going to try Mobil 1 (15w-50) at this change. I haven't noticed any clutch slippage with the HP4M, so I'm going to assume that Mobil 1 won't cause any problems either. What oil are you using, and how often are you changing it?
Keep upright and in the wind..........Pacman