I've rode dirt bikes and crotch rockets for many years. One very important thing I've learned is that synthetic oils are not good to run in a crankcase in a motorcycle. As a two stroke oil is a different thing. In a crankcase, synthetic oils are too slippery and will cause wet clutches to slip. When they slip, they wear out. Everyone that I knew riding crotch rockets that ran synthetic would be replacing their clutch every 10K miles. Those that ran motorcycle oil never replaced their clutch. Those clutch particles are too small and will go right through the oil filter and defeats the purpose of using synthetic. I've seen it with quads and dirtbikes too. I've tried to tell everyone not to use synthetic in motorcycles and nobody listens. In fact, automotive oils will do the same thing because they use friction modifiers. All motorcycle manuals will state to only use motorcycle oil, but who reads manuals? Motorcycles oils have wear modifiers instead of friction modifiers and are designed to be used with wet clutches. They key to motorcycle crankcase oil is to change often. Since cars don't have wet clutches, they can use any oil without worry of damage. Some of the Honda dirtbikes had an important difference, they had two oil galleries. One for the clutch and transmission and a seperate one for the engine gallery. This keeps the engine oil from getting those very fine contaminants from the clutch and the transmission from getting into the crank bearings and the cams.