How can you jump mower while sitting on seat (to engage seat safety switch) when charger cables are hooked to battery under the seat? I have clutch pressed down and in its locked position but do I have to press seat switch since I am jumping it and the seat is up? Motor turns over about 3\4 turn usually stops when fly wheel gets to the magnet. This happens even when jumping or with a good battery charger. I checked shear pin and its OK. Pulled plug it was wet with gas. Dried spark plug then checked for spark none. I can physically turn flywheel past hard spot then try starting again it turns over 3/4 turn then stops. Carburetor makes a popping sound while turning over but engine never seems to fire. I could use a couple extra hands while attempting to start this beast. Don't know how to check voltage while starting, pressing the seat switch holding down clutch and try to hold voltmeter cables on necessary locations.

This might be too much for you... but. Try removing the head and cleaning the carbon out and re-seat the valves. Then manually turn the engine over and verify that the valves are properly functioning .wipe valve heads and entire cylinder and head with acetone before closing up

Also you can disable all safetys by un-plugging the round connector with black wire coming from under the shroud.usually near the starter