Yanis,
Sorry the easy fixes didn't work.
Sounds like the Ignition circuits are OK. Check the compression on both cylinders. they should be nearly the same. If the compression in one cylinder is much lower than the other, You could have stuck rings, burned piston, or other things wrong in that cylinder. It's not likely a bearing. When they go, it's usually terribly obvious. Compression should be somewhere between 110 psi and 140 psi. The important thing is that they are about the same.
The fact that it all started so suddenly still makes me think it might be a carb. It takes a little work, but if you switch positions with the carbs and one is bad, the dead cylinder will follow the bad carb. Just take the top off the carbs and pull out the slides, Pull the fuel lines off and reverse the carb bodies. then put the slides and fuel lines back in the reversed bodies. If the dead cylinder has changed positions, you know its the carb.
Are you using the chokes on the carbs? If so it could be that. They are not really chokes, but enrichener circuits. If one is stuck open, it could be flooding the carb. (some use them, some don't. Mine were disconnected and I just used the primer)
1. check the compression, if thats OK:
2. reverse the carbs. If the problem moves with the carb, a carb teardown and complete inspection and cleaning is in order.
If the compression is too low, you can pull the exhaust manifold off and inspect the cylinder wall and the rings. Look for scoring and aluminum deposits on the walls. It's hard to see the ring clearance but if you put oil on your finger and rub it on the exposed rings, you can see the oil squeezing in and out of the rings as you move the piston slightly up and down. This usually indicates that they are not stuck.
I'm still hoping its a carb problem
Bill.
