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!
You set the valves a .004 inch? Do you have the old fuel solenoid from the carburetor? Take it and remove the working tip, and install it in the carburetor as a dummy, and run test.
I would go back and check the valves again, turn till one valve is spring compressed, (open) and check the one that is up. Then if it is ok, turn till the ok one is spring compressed and check the other. You don't need to even remove spark pug!
You are not getting enough fuel thrugh the carburetor. I would try the old fuel solenid , with the tip off, to see if it makes any differnce. Is this a gravity flow tank to he carburetor, or is there a fuel pump between? Is fuel pump working?
You are choking the engine, with hand, and making it run richer, the black smoke so it is not getting enough fuel through carb.
Did you remove the flywheel to check the timing key?
OK> I will opt out and see if someone else has seen this! Sorry.