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John Deere GX 335 runs rough, excessive black smoke

#1

E

elmrfudd

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!


#2

R

Rivets

Check your oil level and if it smells like gas. If so you have a carb flat needle that is not sealing properly. If not the problem I would be testing for blown head gaskets on both cylinders.


#3

H

hlw49

Make sure the air filter is clean and the choke is working properly.


#4

E

elmrfudd

Rivets said:
Check your oil level and if it smells like gas. If so you have a carb flat needle that is not sealing properly. If not the problem I would be testing for blown head gaskets on both cylinders.
Click to expand...
That was my suspicion when my brother explained the symptoms from the get-go, and I changed the oil anyway just in case that was the issue. Oil level then was just slightly over the full mark. I just checked the oil level, and it’s a little below the full mark, and just smells like pure oil, so I’m ruling out the leaky carb. I’ve seen the leaky needle/seat situation before, where the crankcase was way over the full mark, oil super-thinned out, and obvious gas smell coming out the filler tube. This is not the case here. I’ve also changed many blown head gaskets over the years, and there are none of the obvious symptoms of such, like the hissing sound or heavy blue smoke. I do have some shop experience, and have seen similar symptoms, but I suspect something deeper going on here. I don’t have a ton of experience with Kawasaki engines, so was wondering if this issue might be more common with the brand. Also, the air filter is not brand new, but reasonably clean. What my biggest question is, is why was it running great for my brother for twenty minutes, then all of a sudden it was like someone put it into full choke mode? Thanks for your input guys, and I really appreciate it!


#5

B

bertsmobile1

probably crud stuck under the float needle
The dim witts in the EPA decided that the carb bole overflow / vent had to be internal so when the float bowl overfills the fuel flows out of the hole in the back of the carb and directly into the engine manifold giving you an effective main jet of .125" about 50 times the actual main jet size .


#6

E

elmrfudd

Well, because of my suspicions that the gas was making its way into the oil, the first thing I did was remove the carburetor, strip it down, and put it in my ultrasonic cleaner for two hours at about 160 degrees. Needle and seat were extremely clean when done, so there’s no crud. I searched the web for a carburetor kit for this engine, with no success. Plenty of cheap aftermarket carbs out there, and found some OEM carbs for $300+. That’s an expensive part to put into an old mower to risk a possible hit and miss repair. The internal carb bowl overflow/vent does make sense regarding making the mixture super rich, but this mower will sit running at idle all day long, purring like a kitten, with not even a hint of black smoke. I would think with that much internal fuel in the carb/intake, it wouldn’t idle at all. So bertsmobile1, this could very well be a design flaw common to Kawasaki engines, in your opinion? I am open to an additional cleaning and new needle and seat if I can find a kit anywhere for this carb. Typically, after cleaning the carbs, I polish up the inside of the seat with a Q-Tip with a little toothpaste, and make sure there’s no lint or toothpaste left in the seat when I’m done. I’ve always had great success with that process. Thanks a bunch!
bertsmobile1 said:
probably crud stuck under the float needle
The dim witts in the EPA decided that the carb bole overflow / vent had to be internal so when the float bowl overfills the fuel flows out of the hole in the back of the carb and directly into the engine manifold giving you an effective main jet of .125" about 50 times the actual main jet size .
Click to expand...


#7

E

elmrfudd

elmrfudd said:
Well, because of my suspicions that the gas was making its way into the oil, the first thing I did was remove the carburetor, strip it down, and put it in my ultrasonic cleaner for two hours at about 160 degrees. Needle and seat were extremely clean when done, so there’s no crud. I searched the web for a carburetor kit for this engine, with no success. Plenty of cheap aftermarket carbs out there, and found some OEM carbs for $300+. That’s an expensive part to put into an old mower to risk a possible hit and miss repair. The internal carb bowl overflow/vent does make sense regarding making the mixture super rich, but this mower will sit running at idle all day long, purring like a kitten, with not even a hint of black smoke. I would think with that much internal fuel in the carb/intake, it wouldn’t idle at all. So bertsmobile1, this could very well be a design flaw common to Kawasaki engines, in your opinion? I am open to an additional cleaning and new needle and seat if I can find a kit anywhere for this carb. Typically, after cleaning the carbs, I polish up the inside of the seat with a Q-Tip with a little toothpaste, and make sure there’s no lint or toothpaste left in the seat when I’m done. I’ve always had great success with that process. Thanks a bunch!
Click to expand...
I did find a 16030-7002 float needle valve on eBay for $23. It may or may not resolve the issue, but will hold off a bit until I get more input from the fine people on this forum. I have a full plate the next couple of weeks, which would allow a little time to gather some more comments. Again, I’m very appreciative of any insight that’s shared here. I really enjoy the knowledge and expertise I see on this forum.


#8

S

SeniorCitizen

Can we eliminate a air filter problem by running it without the air filter for a few minutes ?


#9

E

elmrfudd

SeniorCitizen said:
Can we eliminate a air filter problem by running it without the air filter for a few minutes ?
Click to expand...
Absolutely did that. As a matter of fact, right after reinstalling the carb after cleaning, I left the air filter off. Runs the same with or without the air filter.


#10

Tiger Small Engine

Tiger Small Engine

elmrfudd said:
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 a 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!
Click to expand...
A Kawasaki engine with 8100 hours on it should be in the Hall of Fame.


#11

E

elmrfudd

Tiger Small Engine said:
A Kawasaki engine with 8100 hours on it should be in the Hall of Fame.
Click to expand...
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. 🤔


#12

Hammermechanicman

Hammermechanicman

Have you checked the crankcase breather?


#13

E

elmrfudd

Hammermechanicman said:
Have you checked the crankcase breather?
Click to expand...
Actually, I have not checked the crankcase breather. Could you please expound on that a bit? Thanks!


#14

Hammermechanicman

Hammermechanicman

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.


#15

StarTech

StarTech

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.


#16

E

elmrfudd

Hammermechanicman said:
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.
Click to expand...
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. 😊


#17

E

elmrfudd

StarTech said:
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.
Click to expand...
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.


#18

D

Dwayne Oxford

Sounds like the main jet came loose.


#19

1

1fixitman

elmrfudd said:
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!
Click to expand...
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?


#20

E

elmrfudd

1fixitman said:
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?
Click to expand...
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.


#21

1

1fixitman

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.


#22

StarTech

StarTech

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.


#23

E

elmrfudd

Here is the exploded view of the carburetor on this engine, to let all of you know what I have. It is a different carb than the one posted above in the link. Thanks for the posts, guys!

Attachments





#24

StarTech

StarTech

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.

1717416112222.png-


#25

E

elmrfudd

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!


#26

E

elmrfudd

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!


#27

E

elmrfudd

elmrfudd said:
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!
Click to expand...
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.


#28

E

elmrfudd

elmrfudd said:
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.
Click to expand...
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.


#29

I

ILENGINE

@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.


#30

E

elmrfudd

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


#31

Tiger Small Engine

Tiger Small Engine

elmrfudd said:
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
Click to expand...
4 ounces of water in the tank will definitely cause problems. Drain the carburetor also, if you found water in the the tank.


#32

E

elmrfudd

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


#33

E

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!


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