My LA110 John Deere Lawn Tractor with a 19.5 hp Briggs and Stratton motor is having trouble strarting. The engine will crank about 3/4 of turn then seems to bind up. If I manually help the motor turn past the bind point it will spin normally for another 3/4 turn. The electrical starting system (battery, cables, etc.) are all fine. It acts like there is too much engine compression to start. Any ideas?