Spark Plug Interpretation
- Thread starter Gebo
- Start date
That little bit of soot built up on the insulator is nothing. It's likely residue from running the machine with the choke on for start up. Had you run the machine under load for a while, chances are it would likely burn off.
What's interesting though is that only one plug has soot on it as though only one cylinder was receiving more fuel?
The sooty plug's electrode appears to be whitish. Which isn't unusual in today's lean running engines.
You have nothing to worry about. The plugs look fine.
The best time to read a spark plug is after running the engine under load for a good period of time. Normally the color should be a tan. But, as I said, today's very lean engines often show very light deposits.
I have a 2005 Craftsman riding mower powered by a Honda GX engine. In the thirteen years that I've owned it, I've yet to pull the spark plugs. Engine starts quickly and runs strong. I've never felt the need to take a look at the plugs. Maybe this year.
That would make sense with one cylinder behind the other in a vertical installation. Especially in an air cooled engine. But in a horizontal, fan cooled V-twin, I doubt there would be a significant temperature differential between cylinders requiring different jetting and if the engine only has one carb, I'd say we can safely rule that out.
You should run the tractor at full rpm and mow. Then shut off the gas to kill the engine and pull and check the plugs.
Originally Posted By: Lubener
You have some oil control issue, compression or weak ignition associated with that one cylinder. That left plug is not acceptable and should look like the other. I have an old craftsman twin that did that, but not as bad, it was a bad magneto coil.
Originally Posted By: boraticus
Originally Posted By: Lubener
You have some oil control issue, compression or weak ignition associated with that one cylinder. That left plug is not acceptable and should look like the other. I have an old craftsman twin that did that, but not as bad, it was a bad magneto coil.
Last edited:
Originally Posted By: Lubener
Originally Posted By: boraticus
Originally Posted By: Lubener
You have some oil control issue, compression or weak ignition associated with that one cylinder. That left plug is not acceptable and should look like the other. I have an old craftsman twin that did that, but not as bad, it was a bad magneto coil.
No oil consumption. Years ago I had a lot of misfiring problems. After talking with local dealer, changing plugs, etc., I ended up replacing both coils thinking it was low voltage. Come to find out I had a much simpler fix that I only figured out on accident. For years I had been washing and replacing the foam filter which covered the expensive paper element filter. The paper looked fine so I kept on using it and just washing and re-oiling the foam filter.
Well, guess what? All my problems were fixed when I replaced the paper filter with a new one. It had gotten clogged with dirt that could not be seen with the naked eye. The clogged paper filter had been restricting air flow causing misfiring. Now I change both air filters every two years along with my gas filter and spark plugs. And only with Honda OEM.
By the way, this is the GXV 620, V Twin, 20 HP Honda engine.
Originally Posted By: Gebo
No oil consumption. Years ago I had a lot of misfiring problems. After talking with local dealer, changing plugs, etc., I ended up replacing both coils thinking it was low voltage. Come to find out I had a much simpler fix that I only figured out on accident. For years I had been washing and replacing the foam filter which covered the expensive paper element filter. The paper looked fine so I kept on using it and just washing and re-oiling the foam filter.
Well, guess what? All my problems were fixed when I replaced the paper filter with a new one. It had gotten clogged with dirt that could not be seen with the naked eye. The clogged paper filter had been restricting air flow causing misfiring. Now I change both air filters every two years along with my gas filter and spark plugs. And only with Honda OEM.
By the way, this is the GXV 620, V Twin, 20 HP Honda engine.
Originally Posted By: Gebo
boraticus,
You make an excellent point about oiling the foam filter. I know when it is still in the plastic bag there is a little oil in there with the filter. Maybe I was over oiling it. I'll start a new thread on the "oiling the foam."
