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wm_simpleton

Fouled out plug

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wm_simpleton
This is probably going to be an easy one for this group. I have an Agco Allis 918H with a Kohler CH18S. The right side plug keeps fouling out (as you are seated on the tractor). I noticed about a month ago, I substantial build up of black soot on the front of the tractor after mowing an acre. I cleaned the air filter, and found the plug fouled and cleaned it up. Since then, the black soot on the tractor after mowing has decreased dramatically, but today the tractor stalled and would not start until I cleaned that pesky plug. What am I dealing with.... a bad plug, plug wire, valve or worse... a ring???wah Your comments and guidance is much appreciated. -Joel

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DMedal
Yeah, easy for us, then you get to fix the tractor! Here's where a picture is worth a lot more than words. What's the plug fouled with? Oil (black, greasy)? carbon (black, sooty but dry)? -Don

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wm_simpleton
I just swapped the plugs to switch sides and see if it would follow thei plug or stay with the cylinder. Here is a picture of the plug after 40 minutes of mowing while in the original cylinder. In my unprofessional opinion, it would be black and greasy. But I have to scrape the black off to clean it up. Cannot simply spray with a solvent and wipe off. The tractor does use about a quart of oil per month of summer mowing.


Sorry the picture is so big, still getting feeling my way through what looks acceptable!!! -Joel

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DMedal
quote:
Originally posted by UCD
Bad Intake manifold gasket on that cylinder or bad oil ring.
The head gasket is quite a bit easier to check so start there. Maynard, if it isn't the gasket, is replacing just the ring practical or is it a candidate for a total rebuild?

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olcowhand
The pic is blurry so hard to distinguish. The black soot sounds like rich fuel mixture, but the quart of oil is definitely a sign of worn oil control ring. You can have great compression & still burn oil if the oil ring is worn. Gas fouling is harder on plugs than oil. My BIL had a cylinder start cutting out real bad & his spark plug fouled out. Turns out his ignition coil was getting really weak. Yours sounds like a combination of worn rings & rich fuel mixture. I'd get a brand new air filter, then tweak the main jet screw till she's dead-on. If you can't get into a rebuild (if needed) for a while, they make "oil burner plug inserts" that screw in where spark plugs go, then the spark plug screws into it. This keeps spark plug further from the gas swirl & the spark plug will last much longer. I had to use on on my Chevy Blazer till I could tear into her & my spark plug NEVER fouled after the insert.

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Willy
It could be your rings are cabined up from a rich mixture, I would suggest be for tearing into it you take the plug out and spray some good carb cleaner in the plug hole and let it soak for a little bit, then stick a good plug in and run it hard for awhile. If the ring are sticking because of carbine it may loosen them and it don't cost nothing but time if it don't help. I would also check intake gasket for leaks and lean up the mixture if you can.

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RayS
I would start with the head gasket. I had this exact same problem with my kohler command. The head gasket blew and that cylinder used alot of oil and fouled the plug. It would go thru a quart of oil fast. The cause was from not shutting it off at 1/2 to full throttle. I would turn it off at a idle and the gas would ignite in the muffler and cause it to backfire at shut down. I now shut it of like the manual states and I haven`t had a problem in the 2 years since the dealer fix it.

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bluecap24
I would agree that it sounds like a head gasket. I had the same problem with my sunstar and Ch20. Mine would loose power after it would warm up. Changing the gasket wasn't hard, but the way mine was mounted it had to be removed from the tractor. A little advice if you tear into it do both sides.

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wm_simpleton
Finally had the time to tear into this problem. Many thanks to my neighbor, who is a member of this forum, but would rather not be mentioned in case the engine detonates when we start it back up.wah We replaced both sides as someone suggested. One side look rather normal in my uneducated opinion. But the other looks as though it was having issues. The odd part is that my memory says that the side in the pictures was not the side fouling out the plug. But... I am pushing 40, so keep that in mind. :D Here is the first thing that looked out of place. Not sure there should be that much darkness around the exhaust valve. One thing to note is that the head bolt you see missing in the picture came out very easy, as did the one directly above that. The two on the opposite side of this head were a little more work.


Here is a shot of the top of the cylinder wall. You can see what appeared to be exhaust gas patterns on the heat fin where it may have been leaking. Does anyone agree with this?


Here are both of the head gaskets that were removed. As you can see by where we are pointing, they do not match. The one on the right of the picture was on the suspect side. Add this clue to the head bolts taking little effort to remove and I would say that this side had been replaced before. The gasket on the left matches the new ones that came in the Kohler kit that I bought. Am I way off base here? I need to take another look at them. After reviewing the pictures, the one on the right almost looks like a smaller diameter. but it may the be the angle of the picture.




Thanks for all your collective thoughts thus far. This is a truely valuable group to be a part of. -Joel

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wm_simpleton
Both pistons had some carbon build up similar to what you see in the pictures. Given that the engine has 10 years of use on it, I have been told that is not out of the ordinary. The cylinder walls appeared to be in good shape, no apparent grooves (right term?). The cylinder with the odd gasket may have been a little worse, but not by much. -Joel

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wm_simpleton
Finally has some more time to finish putting the engine back into the frame this eveing. I took another picture of the old gaskets, and I am not crazy. The cylinder diameters on the two are different. Here is a picture of them both with the odd one on the bottom. You can see the difference pretty clearly


-Joel

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