When spark plugs go bad - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 5 Old 09-24-2011, 07:49 PM Thread Starter
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When spark plugs go bad

My Craftsman GT has been running poorly for a while. Ran fine on start-up but within a few minutes it seemed to be missing and had less power.

Thought it might be bad gas so I drained and re-filled. No luck.

Looked at the fuel filter and, even though it didn't look too bad, I replaced it. No luck.

Pulled the plugs and they looked good (to this untrained eye) but I checked and re-gapped them. No luck.

Finally, I replaced the plugs, even though I had put new ones in this spring. And ... voila ... running like new again.


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post #2 of 5 Old 09-24-2011, 08:01 PM
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Re: When spark plugs go bad

Even different manufacturers of plugs give different results.
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post #3 of 5 Old 09-24-2011, 08:36 PM
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Re: When spark plugs go bad

Yeah plugs can make alot of difference. I looked at mine today and it was FILTHY. I cleaned it up and regapped it and now the tractor runs alot better. I really need a new plug considering I've never changed it before, but it will work until I get a chance to get one.

1973 Sears ST16 (48" mower deck, front plow, snowblower, litter whisk, broadcast spreader, manual 3 pt hitch, penn line dump trailer)
1964 Bolens Husky 900 (38" mower deck, front plow, home made dump trailer)
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post #4 of 5 Old 09-24-2011, 09:45 PM
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Re: When spark plugs go bad

I'd say bad plugs are one of the most over looked,easy repairs one can make--now how would I know that??

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post #5 of 5 Old 09-25-2011, 01:38 AM
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Re: When spark plugs go bad

They ARE important--especially when you only have ONE...a single cylinder engine needs one that works,isn't fouled,and has no cracks in the porcelain to short the spark to ground instead of firing at the tip...you aint got 3,5,or 7 other cylinders to run on like a car when one dies--one dies,its DEAD!..

I've had plugs last decades,others I've had "die" suddenly,like a switch went off inside them,and though they'll spark outside of the engine fine,they would not let it start when put back in--tried a new one and VROOM,cured!!..I've had some plugs "shut down" after they get hot,then work again once they cooled down..(I smash those so I wonrt end up using them again !)..

I think some magnetos get flukey too though,and make the plug look "bad",but putting a new one in or reducing the gap on the old one can mask a weak magneto,as the new plug has lower resistance,and the smaller gap is easier to jump..

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