JD 60, why did my left side spark plug gap disappear?

pmarkel · Mar 5, 2018

Sorry this is a long one guys. I noticed my JD 60 was running a bit rough today, like it sounded hollow or lean. Now I set the carb the way I wanted it two falls ago and haven't touched it since so I couldn't understand how it could be running too lean. I adjusted with the idle needles but that made no difference. I did the manifold a month ago but was careful especially where the intake was concerned that it wouldn't be sucking air. For the heck of it, I removed the spark plugs which had maybe 200 hours on them (autolite 3116). One looked fine. The other one had literally no gap--you couldn't even fit a piece of sandpaper between the electrode. Now this tractor ran great, idled well, started fine all last summer and fall plowing, raking, and shredding corn. It seems odd to me that I wouldn't have noticed it getting rougher. What might cause a once gapped plug to close on itself? The only thing I can think of is incorrect advance on the spark timing on the distributor or valves lash adjustment but I don't know whether that makes any sense and you certainly don't hear any noise on the valve train on this tractor. Thoughts?

Pete

Russ from MN · Mar 5, 2018

Not sure how the clearances are in that engine, but possibly a loose piece of carbon bounced around and closed it. I had something like
that happen with a 46 Dodge flathead 6.

pmarkel · Mar 5, 2018

I am not sure about clearances having never tested its compression. The tractor has only about 3300 hrs on the hobbs hour meter and unlike some of my other tractors, it seems to have very marginal wear. It has always had plenty of power and will pull an Oliver 3x14 through our clay soil. I should also have noted that when I did the manifold job I had to cut the old manifold quite a bit around the studs/cap screws to get a good hold of them but I thought I had been careful not to cut near the intake manifold as there was quite a bit of dust and dirt created and I did not want that to get sucked in the intake valves. When I cleaned up and regapped the plug I started her up and she sounded great again.

susandiane · Mar 5, 2018

I agree that something in the cylinder mechanically smashed the plug "shut", there just isn't any other possibility unless you've got someone messing with your mind. I'd say that since it didn't break the porcelain of the spark plug, it wasn't a chipped off edge of piston or valve or something hard. I did have an instance once of a throttle or choke plate screw that got into a cylinder, but it caused a lot more damage than that before it blew out the exhaust. I think the carbon explanation is 99.9% probably correct. In which case, forgetaboutit.

jd man wis · Mar 5, 2018

When you work it hard will the tractor ping. We had a g that my dad ran fuel oil in it was set up to run the fuel because it had the manifold on it to burn the fuel but it would ping bad if you worked it hard in like to high of a gear. It would blow the end of the spark plug off and it would not start in the next time you wanted to use it because off the ends gone. We pulled a three bottom plow in 1 or 2 gear so it wouldn't do the ping. Switch it over on gas and it would pull the same plow in the same area in 4 gear ?. After a head gasket later in the years we notice that it had high compression pistons in it and fooled us on the fuel that should be run in it. It didn't matter tho the old man ran the fuel oil in it any way and when I asked him why he said that if he didn't he could not afford the gas to run it. It might be that them pistons were replace or iv tore some apart that had two different pistons in them and one will travel up closer to the head.

ET · Mar 6, 2018

I think a piece of something got into the cylinder when you did the manifold job and bounced around till it hit the spark plug. I would pull the plug and get a bore scope and look around in that cylinder.

Resting Relics 1 · Mar 6, 2018

Pete,
Funny reading your story. I had a JD A that I replaced the manifold on. Had quite a time getting the studs out. I slide the manifold up as much as could and used a saz-all to cut the studs off leaving enough so I could get a vice-grip on them. Heated the head and got them out. When I got it back together and I started it up it sounded like it had a serious rap that it didn't have before. I pulled the spark plugs out and noted the left one was beat up bad and the gap was closed up. I rolled it over by hand till the piston was near the spark plug hole. I stuck a magnet through the hole and came out with a short piece of stud. Evidently it rolled in to the intake when I had the manifold off. Long story short. Your story sounds the same. I bet a piece of something got in there when you were doing your manifold work and it slapped around in there beating up the plug. Good Luck!
John

JD 60, why did my left side spark plug gap disappear?

pmarkel

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Russ from MN

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pmarkel

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susandiane

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jd man wis

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ET

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Resting Relics 1

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