Typically, engine flushes should not be used in motorcyles. They have detergents and other ingredients that can be harmful to the clutch fibers, and since motorcycle engines generally have much tighter tolerances than car engines, the flush can actually remove enough of the oil's lubrication abilities to cause excessive friction and damage to internal parts. The best way to "flush" a motorcycle engine is to start the engine and get it nice and warm, possibly even ride the motorcycle for a short distance, and then drian the oil and replace the filter. After filling with fresh oil, run the bike for a few minutes and check the oil. If the oil still seems dirty or dark, repeat the oil drain and refill process again. This is a little more expensive than a "Flushing" product but it is the best and safest way to flush your engine.
