How can I get my Craftsman garden tractor to start?

When I turn the key to start the engine cranks with an effort.
I've replaced the fuel filter, battery and starter three months ago and it's still difficult to start. It started okay with difficulty after putting in the replacements. Now when starting to crank it it's difficult and won't even turn over. When I crank it too many times the starter assembly on the outside gets hot. Last week, I put a charger on the battery and it's not the battery as it's still difficult to start the tracor.
I have the Craftsman DYT 4000, which I bought new three years ago. The tractor has 80 hours on it. The model number is 917 2736401.

CAN ANYONE OFFER SUGGESTIONS TO START THE TRACTOR AND SAVE ME MONEY WITHOUT HAVING TO CALL A SEARS REPAIR PERSON.