"Sometimes it tries to start & acts like it has too much compression" What does it do the "other" times? Is this a gravity feed carb that might be leaking and filling the cylinder with gasoline? Smell the oil in the crankcase and see if it has a gas smell. Have you had the battery load tested? Have you cleaned all connections in the crank circuit, including grounds? This includes engine mounting bolts. What tractor is this on? /'

Check battery and connections. Connections need to be clean and tight. Charge battery, do a load test on the battery. Use a known good battery (booster /jumper cables) to try to turn over engine) but make sure you have good connection and correct polarity. Batteries seldom last past 3-5 yrs. There's a reason why stores are stocked with lawn tractor batteries this time of year.

Your concern about the valves is based on the brief opening of the exhaust valve? What you are seeing there is the action of the compression release (ACR). This is only supposed to occur at cranking speeds (or lower) and when the engine RPM increases, the ACR is disabled. Have you been noticing any black smoke out the exhaust when the engine is under a load? Is the "black carbon like substance" shiny and sticky, or is it dull and powdery looking? Shiny & sticky indicates oil consumption through the combustion chamber. This could be due to a worn engine or it could be due to a leaking head gasket (leak between combustion chamber and pushrod gallery) pressurizing the crankcase, which will force oil into the intake manifold. If shiny and sticky, you need to do a "cylinder leak down test". If not equipped to do a leak down test, you need to pull the valve cover and watch the space down inside the pushrod gallery while the engine is running. Shine a powerful light in there and watch for regular puffs of compression blowing into the gallery from the combustion chamber. If dull and powdery, the engine is getting too much fuel..........or too little air.

For those who might be interested. I have come to the conclusion that someone has changed carbs on this engine. I got the schematic, and even though the colors don't match the schematic, there is nowhere for the extra hot wire to go except to a shut-off solenoid. I put some heat shrink on the wire terminal, and took the mower back to the pastor. Thanks for all the help, guys. EJ