# JD X584 Lawn Tractor Fouling One Plug



## Pauly (Jul 3, 2017)

After only about 10 hours, my new X584 started running rough and would even backfire. One of the 2 plugs had a heavy buildup of dry black carbon but the other one looked pretty normal (no carbon). I had been running too much at idle speed, so I started running it faster. I now have 45 hours on it and just changed the plugs again. As before, one plugs has a significant carbon build-up but the other one seems normal. I run 91 octane or higher. Does this sound like a carburetor issue? I’ve been diligent in running at a high RPM since the first event...


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## pogobill (Jan 31, 2012)

With that hydro-static drive, you should be pretty much running it at full throttle. Sounds like a carburetor issue of running too rich, but you'd think both plugs would foul. Are both spark plugs the same? The fouled plug may be a colder plug.
Hope it's not piston rings in the one cylinder!?!


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## Pauly (Jul 3, 2017)

Both plugs are the same and gapped the same. Since the condition occurred both with the original factory plugs and one set of replacements, it doesn’t seem to be the plugs themselves. Would there be a ring problem right from the factory? (Problem originally showed itself with less than 10 hours on the engine)...


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## pogobill (Jan 31, 2012)

So it only has ten hours on it? Probably not a ring issue, at least one would think not. Fouling plugs could be a carb issue, running rich.
I'm sure someone will pop in and help you more than I can, most of my gear is getting up in years!
Welcome to the forum, by the way. Hope we can help you with your problem.


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## RC Wells (Dec 26, 2008)

Dry black carbon is fuel related, not oil related. Run the mower with the throttle full open and regulate your speed with the hydrostatic pedal. Other than ruining your hydrostatic transmission from low fluid operating pressure with partial throttle operation, the engine is consuming fuel in what it senses as the start or warm up mode and runs rich with cool combustion temperatures.
If operating it wide open causes it to continue to build up soft carbon on the plug in question, you will need to go back to the dealer for warranty work.
Keep us posted.


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## Pauly (Jul 3, 2017)

What should I learn from the fact that only one plug has the carbon buildup? Can an air/fuel mixture adjustment be made on only one cylinder? I've been fairly diligent in running the engine at nearly full throttle (in the "green" zone)...


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## RC Wells (Dec 26, 2008)

There are two versions of this Kawasaki engine used in that series of mower, one is equipped with a two barrel carburetor (one for each cylinder), the other is fuel injected and generally does not have fueling problems.
If you have the carburetor equipped version, the answer is yes one cylinder can receive more fuel than the other. So, if you are running the throttle wide open, and long enough the engine actually performs considerable work when it is fully warmed, it is time to return to the dealer and have the warranty take care of the issue.


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