Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
This is a twin engine, Have you ran a cylinder balance test? Loosen the soar plug wires and with engine idling, remove one wire at a time, engine should continue to run, if engine dies when wire is removed, the opposite cylinder is not firing. Check for spark and compression.
OK, but is it firing on both cylinders?
Both sides the same?
Good spark, fuel is there, compression is good, valves are set. You say it started all at once? Intake gaskets good, not leaking?
I would remove the flywheel and replace the timing key!
No,not a wear part, but if it gets any damage, it throws off the timing and will make engine hard to start.
Did you replace it? It can not have ANY damage.
I see question is still open, did you find probelm? You say it will not start without ether? That makes me think that is is not getting fuel. You say you replaced the backfire solenoid? Take the old one and cut the inner tip off and install it as a dummy, and run test.