https://partscatalog.deere.com/jdrc/sidebyside/equipment/80153/referrer/navigation/pgId/2564950 Look at part 36 O Ring to see if it is damaged and allowing too much fuel into the main jet.
John Deere GX 335 runs rough, excessive black smoke
- Thread starter elmrfudd
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That O-ring being bad would cause the carburetor to overflow with fuel. Items 38 o-rings would fuel the flow pass the main jets. Note be careful not to mix up the main jets.
- Joined
- Feb 19, 2020
- Threads
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- 10,592
The fuel bowl gasket can be damage due compression time or nicks. Whenever I disassemble one these carbs I always replace it. I called it a spaghetti gasket much like the Nikki single barrel fuel bowl gasket that gives similar problems of fuel leakage.
The seat
Also pressure test the float needle valve and seat. It should hold 5-7 psi for 30+ minutes while the carb is inverted. The seat can be clean with six flute counter sink bit of the proper angle. Do not use a countersink with less number flutes. Sometimes it can be just polish up with a Q-tip swab and fine valve grinding compound but I prefer the countersink bit
The countersink will be either a 60 or 82 degree version. Must match the needle valve tip within a degree. And it only way to clean up none replaceable needle seats.
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The seat
Also pressure test the float needle valve and seat. It should hold 5-7 psi for 30+ minutes while the carb is inverted. The seat can be clean with six flute counter sink bit of the proper angle. Do not use a countersink with less number flutes. Sometimes it can be just polish up with a Q-tip swab and fine valve grinding compound but I prefer the countersink bit
The countersink will be either a 60 or 82 degree version. Must match the needle valve tip within a degree. And it only way to clean up none replaceable needle seats.
-Thank you, StarTech for your expertise here. Since I don't have a leakdown test kit or the countersinks, I can however, clean the seat with Q-Tips and grinding compound, along with careful inspection of the bowl gasket. I did find new bowl gaskets and carb needles on eBay, as well. If there's a loss of needle/seat pressure retainment, is it safe to assume it's not handling the pressure from the fuel pump, causing the bowl to flood? Also, what are your views of this possibly being related to the crankcase vent. Still on vacation, but would appreciate your thoughts on this as well. Trying to think a little outside the box on this one, as well, in trying to consider other issues aside from giving the carburetor all of the blame. Thanks!
Well, I’m back from vacation, so I started back in on this JD tractor again. In following Hammermechanicman’s suggestion to check the breather, I removed the wide breather tube from the air intake, and I was able to start, run, and throttle up the engine without the black smoke and rough running, so it’s apparent I have a crankcase breather issue. Does anyone here on this forum have experience with these Kawasaki breathers that can offer tips on what to look for, that could be a probable cause of the running rich issue? Possible crud in the valve? Breather valve failure or damage? Thanks, in advance for input!
I should also note that the other end of this tube attaches to the cylinder head, and not the engine block. Not sure exactly what that entails and whether I’ll need to remove the entire head to address the issue.
In my previous post, I mentioned that the engine started and ran flawlessly, at all speeds, but failed to mention that was with the air filter OFF. Even after reinstalling the tube insert and breather tube, it ran flawlessly, at all speeds. However, when I reinstalled the air filter, the black smoke and rough running resumed. I lifted the air filter for a few seconds, and the engine smoothed out and ran good again. I examined the air filter and pre-cleaner, and could see plenty of light through the paper element, and the pre-cleaner was clean. So I’m guessing this engine still can’t breathe with this air filter, even though it appears clean. I will replace it and see what happens.
@elmrfudd Smell the oil for a gas smell. Gas fumes in the oil coming out of the breather will cause a rich run issue with the air cleaner installed but not when the air filter is removed due to the breather not being captured by the air filter.
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