Lawn tractor engine replacement

Question

I am replacing a 14.5 HP Briggs & Stratton engine with a 17 HP on a Snapper Z- Rider Yard Cruiser. I cannot get the pulley from the main shaft which is all that remains to remove the engine. I have tried using a 3 point wheel puller only to damage the pulley. even after bracing the pull points I got the same results. What am I doing wrong?