Kohler CV18s Crank issue

I just bought a Toro 267H with a CV18s engine. It has been sitting for awhile. I am having an issue with it not fully cranking. It tries to crank. If I remove the spark plugs the engine cranks flawlessly. I first thought that the valves may need adjustment. Well I dont see how to adjust them. I am using a new battery 300. I am going directly to the starter. The tractor needs a new ignition switch. Any help will be grateful.
Thanks