350 running rich

Raking hay with the 350 this morning. Puffs some black smoke when advancing throttle or when governor adds a little. Iturned the load screw clockwise 0ne turn and it bottomed. Ran a little better but still puffs a tad black.
Is this result of float level too high, or messed up mail fuel passage? Is there a jet under that load screw?

Float level most likely, unless the air cleaner needs radical attention. Jim

My M was behaving that way not too long ago. I took the carb apart and found the float level to be just about perfect. Couldn't find anything else wrong, so just for fun, I replaced the needle and seat. That M runs just fine now.

Thanks. Will pull the bowl off and set the float a little lower.
Engine does not hum as it should.
And ooops, it is my Super H , not the 350.
Going out to bale tonight when the alfalfa softens up. Third and last cutting. August rains came too late.

Has to be float, the main jet develops max power with the screw 5 turns out.

Couple of things here. If you truly bottom the load adjusting screw, the engine will stop running. All fuel, low idle, high idle, full load or whatever has to go through that main jet under the load adjusting needle. The main jet is normally a fixed size on that Super H and once you turn beyond about 3 1/2 turns open, it will not restrict the fuel at all. Turning it five turns like recommended for full load is to guarantee you are not restricting the flow. If someone has oversized or installed larger jet then it is possible to overfuel. In that case, running at full throttle , no load, turning in load screw until engine starts to lean out will would be the action to take. Then you can back it out in small increments , like 1/4 turn at a time until you get the results you want. Fuel level will effect the less than full load fuel consumption due to the difference in the point that the main metering nozzle starts to uncover the air bleeds in the nozzle. The best way to check fuel level is to take out the drain plug on carb, install a barb fitting with plastic hose and holding the hose up along side of carburetor, the fuel level should stabilize at 5/8th inch from top of bowl on that carb with engine NOT running.