I own a 2001 rc51. This summer I accelerated from a stop light and broke my chain. The chain whipped around and ripped my clutch cover off my bike. Where the clutch cover attaches to the crankcase was also sheared off, leaving me with a broken crank case. So I started pricing out how expensive the crank case would be. I need an upper and lower. And they appear to be around $1,200. And I would need to pay a mechanic to rebuild the motor. My question is should I replace the damn crankcase or find and buy a used motor? I could most likley do a motor swap on my own. My current motor has 16K. Also can I swap a 2002 or 03 motor on a 2001 bike?