Is the battery fully charged for the roto starter? Just thought i would throw that in there! Like mention already loosen the glow plug a bit, also if flooded the roto starters have a hard time pulling the motors over. Can you turn the fly wheel over? If so then your motor piston and linkage should be good, next you would have to check the one way bearing like mentioned from others! Make sure this bearing is put back together properly otherwise it will just spin freely when starting. Best thing is to just try a few things and look over everything to make sure any of it is working like it should.