John Deere GX 335 runs rough, excessive black smoke

elmrfudd

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A Kawasaki engine with 8100 hours on it should be in the Hall of Fame.
Yeah, not sure if I mis-read the hour meter or typed in too many zeros, but I know that mower has mowed two acres for many, many years. I’ll have to re-check the hour meter and verify the actual reading. So it may or may not qualify for the Hall of Fame. 🤔
 

Hammermechanicman

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Have you checked the crankcase breather?
 

Hammermechanicman

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Don't know about that engine but some engines when the crankcase vent plugs up the crankcase gets pressurized and can cause excessive blowby and cause oil burning and upset the proper air flow in the carb. Just something to check.
 

StarTech

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I suspect that is 810.0 hours.

When OP cleaned the carburetor did he replace the fuel bowl gasket?You can't reuse the old gasket. Also don't mix up the jets.
 

elmrfudd

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Don't know about that engine but some engines when the crankcase vent plugs up the crankcase gets pressurized and can cause excessive blowby and cause oil burning and upset the proper air flow in the carb. Just something to check.
Not real sure how to test the crankcase vent to see if it’s clear or plugged. Also, I’m guessing that if there was blow-by, the oil would cause a different residue on the plugs than black, powdery soot, perhaps even fouling the plugs. There has been no sign of oil burning whatsoever to this point. Also, I was a little off about the hour meter. It shows 8135 hours, so indeed it does qualify for the Hall of Fame. 😊
 

elmrfudd

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I suspect that is 810.0 hours.

When OP cleaned the carburetor did he replace the fuel bowl gasket?You can't reuse the old gasket. Also don't mix up the jets.
I always clean the carburetors myself in my cleaner, and in this case the bowl gasket was not damaged or disturbed. It fit perfectly in the channels upon reassembly. Neither did the ultrasonic cleaning improve nor make the symptoms worse than before. I’m very meticulous when it comes to disassembling and reassembling carburetors, and all parts were replaced in their respective spots. Oh, I guess I wasn’t aware there was a decimal point on the hour meter🤔. I just looked and saw four numbers (8135), so it could have been 813.5 hours. Rats, now if I don’t go out and look again, I won’t be able to sleep tonight.
 

Dwayne Oxford

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  • / John Deere GX 335 runs rough, excessive black smoke
Sounds like the main jet came loose.
 

1fixitman

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  • / John Deere GX 335 runs rough, excessive black smoke
I have my mom’s JD GX 335, with a Kawasaki engine, 8100 hours, (FH601V-CS04, ENO FH601VB29323), and trying to troubleshoot the rough running and excessive black smoke pouring from the exhaust. My brother was mowing my mom’s yard, and after about 20 minutes of mowing, all of a sudden he encountered the black smoke, and the mower barely ran, so he put it away. Both spark plugs had electrodes that were completely covered with black soot. My first thought was that both coils usually don’t fail simultaneously, and each plug was spark-tested successfully. Once it’s running, at idle it runs just fine until I begin to throttle it up, then it struggles with the excessive rich-running symptoms, eventually choking off the engine until it quits. I did drain the fuel tank, which did have some water in it, and added fresh gas, to no avail. I did an ultrasonic cleaning on the carburetor, so I made sure all internal ports were clear, and used compressed air to remove cleaning solution. I welcome an suggestions as to what I can look for next that may cause the “choke and smoke” symptoms. And yes, the choke is wide open and working perfectly. All input is greatly appreciated! Thank you!
Does this carburetor have the plastic insert in the bowl with a complex o ring between the metal and the plastic? The type with a little brass piece in the white plastic? If so......there is a main o ring and a smaller o ring. If you run ethanol fuel it eats up that smaller o ring. On amazon there is a o ring kit with the complex o ring and the smaller one. Make sure you do not lose the brass piece in the white plastic piece. Can you take a picture of the carb with it taken apart? Sounds like it is partial flooding. I know you are detailed in the cleaning of the carb. The other thing that can cause this has been discussed with partial clogged air filter causing too much vacuum on the vent tube and sucking oil and burning it at higher rpm. Are you losing oil level? I doubt a valve adjustment issue would cause the symptoms you describe. You could always remove the vent tube and tape over the hole to the carb and just let it vent to see if it produces the same problem. These are just ideas. A picture of the carb disassembled and a picture of the o rings inside would tell us a lot more. Good day and happy trouble shooting. Is it this type of carb?
 

elmrfudd

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  • / John Deere GX 335 runs rough, excessive black smoke
Does this carburetor have the plastic insert in the bowl with a complex o ring between the metal and the plastic? The type with a little brass piece in the white plastic? If so......there is a main o ring and a smaller o ring. If you run ethanol fuel it eats up that smaller o ring. On amazon there is a o ring kit with the complex o ring and the smaller one. Make sure you do not lose the brass piece in the white plastic piece. Can you take a picture of the carb with it taken apart? Sounds like it is partial flooding. I know you are detailed in the cleaning of the carb. The other thing that can cause this has been discussed with partial clogged air filter causing too much vacuum on the vent tube and sucking oil and burning it at higher rpm. Are you losing oil level? I doubt a valve adjustment issue would cause the symptoms you describe. You could always remove the vent tube and tape over the hole to the carb and just let it vent to see if it produces the same problem. These are just ideas. A picture of the carb disassembled and a picture of the o rings inside would tell us a lot more. Good day and happy trouble shooting. Is it this type of carb?
Thank you for the tips, 1fixitman! Your suggestions make a lot of sense, however, the carb is currently still on the tractor, and I'm on vacation starting tomorrow morning, and won't be able to pull the carb to see about the o-ring and plastic piece until I get back. I did print out an exploded view parts diagram of carb, however. And I will try the suggestion with the breather as well, when I get back. Thank you for the tips! Will keep you posted when I know more.
 
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