Re: Speeditwin 6039 22.5hp only firing on one cylinder

[Tom]

What is the resistance between the two spark plug wires? What is the resistance between each wire and ground?

I’d try to track down a short in the side that doesn’t fire, (or even a blockage of fuel to that cylinder). Since there is only one coil firing two cylinders, the coil is likely good. One way to look for shorts is to ground the good side directly to the motor. Then attach the wire of the bad side to a grounded spark plug and turn the flywheel by hand in a dark area. If there’s a short in the "bad" wire, you might see the spark. It could also be under the flywheel, in which case you’ll need some kind of magneto tester, or fire the coil with an external battery.

Tom