I have a Sears garden tractor with a kohler engine which for its age runs fine, except it won't start. When the key is turned, I hear a strong whirring sound like the starter is trying, but it is not making a connection with the flywheel. I replaced the starter last year, do I need to do that again or is there a simpler, less expensive solution?

You can just replace the bendix gear on the end of the starter. Much cheaper, and easier also, you can usually make this repair without taking the starter all the way off the unit.