Huskee 18.5 hp 42" deck lawn tractor turns over, won't start. Just changed both deck belts. Model# 608, bought used, think about 2003 model. When replaced upper deck belt, it snapped the bottom one! Got new one, now only turns over. Everything else same. I cleaned out fuel lines and fuel filter, put fresh gas in. checked out coil, nothing amiss. Also put in new spark plug and firing fine. My manuals do not go into detail on these issues and I cannot afford someone to fix it. Help!

Check your compression,check your valve clearence