Frank, why do you want to fit an aftermarket starter when the standard one is perfectly ok? Have you increased the compression of the engine? Or do you have a starter problem? You may not cure it with a new unit if there is a problem somewhere else in the starter circuit. I had a problem with my bike, the starter would not engage properly. I cleaned the starter inside and checked the brushes, all OK. I replaced everything else in the starter system including the soleniod, the starter clutch, the actuating arm and spring, and finally the relay. Nothing worked until the voltage regulator/rectifier failed and I had to replace it. Suddenly the starter worked perfectly. The battery had not been charging properly, OK for lights but it never had full power for the starter. It now works first time, every time. Check everything before spending money for no reason!