Re: Thermoswitch
The thermoswitch triggers a buzzer which is gives you an audible alert for an overheated engine. It does not cut out a cylinder.
First thing you should check is compression. It should be in the 100LBS (min) to 150 LBS (max) range. Cylinders should read no more than 10% variance from lowest to highest.
Next thing to check is fuel delivery. Fuel pump and carbs. These are relatively easy to rebuild and not that costly. Verify fuel lines are not clogged or the primer bulb is functioning. If primer bulb colapses while you're trying to get up to speed, this indicates a bad bulb or blocked line between it and the line going to the tank.
Ignition system trouble-shooting can be difficult to pin-point sometimes. I would suggest that you get a manual if you don't already have one. Also some basic electronic testing equipment like a digital volt meter and a DVA adapter.
One other thing, if your prop has too much pitch, it will load down the engine and prevent it from getting up to speed.
