John Deere GX 335 runs rough, excessive black smoke

[Tiger Small Engine]

I just pulled the dipstick to smell the oil, and cannot detect any obvious gas smell in the oil. That was my first suspicion when I got the mower home three weeks ago. I’ve changed the oil since then, and the oil level is still dead on the “full” mark on the dipstick when I checked it just now. Another thought that occurred to me was this…I drained the fuel tank completely and found there was about 4 ounces of water in the bottom of the tank. I drained the carb as well, and refueled with fresh gas. I was thinking of the possibility of the paper air filter element swelling from steam caused by the moisture in the gas. Knowing the effects of liquid on paper elements causing fibers to swell, I can’t rule out that possibility. I will find out once I install a new filter. If the new filter works out, then problem solved. If the new filter still causes the black smoke, then I’ll be open to further ideas

4 ounces of water in the tank will definitely cause problems. Drain the carburetor also, if you found water in the the tank.

 

[elmrfudd]

Yep, I already mentioned in my previous post that I also drained the carburetor.

 

[elmrfudd]

Well, it appears that the problem is licked!!! I installed a new air filter, and it ran smoothly at all speeds with no black smoke. I’m guessing that the fibers in the paper element in the old air filter had gotten wet, causing the engine to “suffocate”, so to speak. Although I can’t prove it, I presume that the moisture in the gasoline was the culprit, causing the air filter to fail. Many thanks to all who have taken the time to give their input. Blessings to all!