I just picked up a bike they said ran ruff so I cleaned the car and started it barely. After running it for a while it went puff, smoke came out intake an spark plug is smashed. Just wondering if it is worth rebuilding engine or changing engine completely. I have a 97 foreman 400 was going to fix other bike for my son. Bike is in good shape, just never tore into one that much before. Any hints or good place to find parts or engine would be appreciated.