I have lawn tractor used for snow remove as well. There are black smoke and I was suggsted to replace air filter. I did. However it does not solve the problem. I noticed that the choke does not have impact when it is open or close. Maybe it is stuck and cause the black smoke? How to make the choke work again?

Hi,
Clogged air filrrt is the most common.
Peace,
Clarke

The problem is too much fuel not enough air. If it is not the air filter it could be the choke is stuck. Try removing the carb and checking everything is free check all the jets in the carb are free and tight. There could be some dirt in the float valve and holding it open thus flooding the engine. If it is the choke sticking fully usually it will stop when it gets warm. The choke flap is the 1 that you can see from the air filter a round disk with a hole in in. whoke on it should be closed and in run it should be open fully. Hope this is some help

To fix choke if its lever operated try lubrication and if cabe the same or may need a new cable