All good suggestions. So it's a daily driver and ran great then out of the blue it's running bad.. And needs partial choke to smooth out.
1) I had a similar problem, the coil wire had come loose and was dangling down below the coil (it's upside down). Could also be a bad coil to dist wire, replace it with a known good one for testing.
2) check all manifold and carb bolts for tightness. All are known to loosen over time. (sounds like it's sucking air).
3) Do you have a separate fuel filter? if so replace it.
4) Verify you're getting good "squirts" of fuel from the fuel pump. Disconnect the fuel line at the carb and aim it into a glass jar or similar, have some one crank the engine It's OK if it starts, it won't run long). You should see a good squirt of fuel. It'll be on/off based on when the pump is pulling fuel then pumping fuel.
5) Pull the carb and go through it. Jerry mentioned the power valve could be sticking, the float could have a restriction or crud is in the passages.
