I just picked up a 1980's Yamaha, possibly a 90 or 50 - cylinder head says 87 cc. I need to remove the engine. The main pivot bolt behind the motor will turn with a rachet, but no matter how hard I hit the end the bolt will not come out. Is there a special trick, or do I just hit harder?

Sounds like the pivot bolt might be rusted in , put an old nut over the threads to protect them and give it some sledge hammer yeeeeaaaaaaaaaaaaaaaaaaaah