Brought an MC28 engine in from Japan. Obviously been out in the wet. The rotor is seized on the crank. Proper machine shop is trying to get it off. Stripped the threads in the Honda rotor puller tool. Made a puller to grab behind the rotor. The rotor is bending and magnets falling off. A 200 lb. mechanic was hanging full weight off a long bar on the tool. It won't budge.

Any suggestions gratefully received?

I had this problem and found to my cost that I had been just tightening the centre of the puller down into the hollow centre of the crank, which just destroyed the crank threads where the rotor bolts on. Need to make sure you have a bolt or something on top of the crank then tighten the puller onto that, it should then break the seal after a couple of turns and also protect your crank.

Thanks Timmyboy. Too late now. after destroying a couple of pullers they welded a nut onto the rotor and made up a slide hammer. I'm sure (yes, of course i am) that they knew enough not to destroy the crank.

If the engine is that state I'd allow for a new crank anyway. Honda have re manufactured them, so should be able to get one through your local dealer.