Don't buy a new carb yet. I think it just might be the fuel solenoid, telling you what's wrong. Just reread the entire post twice then remembered a problem I had a couple of years ago. Check the wiring going to the fuel solenoid and. I think if you look and feel carefully you are going to find a cracked or partially broken wire. What is happening is the wire will short when you hit a bump or turn. When this happens it will kill the ignition circuit for an instant, meaning no spark. Then it will reconnect and have spark. During the no spark period some raw fuel will enter the cylinder causing a rich mixture, and then when the plug fires a lot of black smoke. It will also backfire with this problem, because the rich fuel is still burning when the exhaust valve opens. You will have to look very closely with your fingers. Go slow and be patient. Go luck.
Hey Rivets... this post is almost to a Tee what mine is doing. (Exmark 25hp Kohler command) just started doing this a week ago, Slight black smoke under load, will backfire occasionally, Loss of power drastically starting to mow anything. will sutter when I hit a bump and puff a black smoke like it's over full. still has problems starting have to choke and then quickly release choke.
Here is what I've done so far... new plugs, air filter, fuel pump, fuel lines. I'm thinking of getting a new carb 30.00, that would take care of solenoid, float and highspeed jet. I'm really struggling here and would appreciate any advice, thanks Michael
