I just recently inherited the Craftsman LT 400 riding lawn mower and just starting to use it this spring. Having a problem with the clutch when I let out on the clutch to move the lawn mower jumps and then settles in to the speed I have chosen with the gear. It does it every time I press in and then let out on the clutch. Can anybody diagnose this issue as to where I start looking to resolve the issue? I would appreciate some knowledgeable help.