kohler courage engine sv590 19 hp

I have this engine in a troybilt (mtd made) bronco mower. was mowing today and it started sputtering with black smoke coming out of the exhaust. I shut it down. I tried to restart it and it is backfiring through the carb. I had been mowing for about an hour. I am wondering if a valve stuck or bent push rod? I need this mower running, I have too much to push mow. Thanks for the help.

Frank

Black smoke is too much fuel. Something blocking the air intake system or needle valve in carb stuck open allowing too much fuel.

backfire through the carburetor is a sign of the valve not sealing for some reason. Remove the cover over the engine. Is there a lot of dust or grass packed in the cylinder head area? Take the valve cover off, look for excessive valve train clearance. (normal should be .004-.006.) Also look down through the springs. Are both the valve guides sticking out the same from the cylinder head?

Since you were mowing and it happened all of a sudden, carb float could have gotten stuck, allowing flooding, probably no backfiring unless you had a lot of carbon buildup (glowing to produce ignition) and lots of fuel leaking into the combustion chamber.

Next, backfiring through the carb says something is allowing combustion pressure to come back through the intake system....aka as stated intake valve sticking would be a starter.

A leaking head gasket on an air cooled engine would, if anything (WAG) detune the combustion process with more air (not much) than fuel in the mix (just the opposite of a black smoke condition), loss of power, loss of compression and performance, no backfiring, maybe hard to restart, not black smoke.

A partially sheared Woodruff Key in the crankshaft-flywheel interface would retard the timing (doesn't take much BTDT) resulting in loss of power. That would also impede starting. If you see anything but a perfect square when you look down at it, replace it. Don't see it as a backfiring source as delaying the ignition during the power stroke has no effect since both valves are closed for the duration of the stroke.

Just my off the cuff thoughts.