Your crankshaft is the beating heart of your scooter engine. It cops the full force of the opposing motion of the piston, and is fully responsible for converting this to rotating motion. Though crankshafts are a a very strongly built part, they do wear over time. Big end bearings wear, as well as the eye which the small end bearing locates in. Bad engine failures can also damage the crank, such as small end bearing failure and main bearing failure. We always recommend replacing the crank bearings and seals when doing a crank rebuild.
