Sparks plugs for a lawn mower.

Gaylord Q Tinkledink

Registered User
Apr 29, 2018
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29,677
Lawn mower died. It isn't the best one, but it seemed like the spark plug was done. However, I can't find the exact one I used before and can't go into stores to measure I bought one online and it's the same length, just the middle and white end are a bit bigger. Is that enough to cause a miss fire/possibly damage to the mower itself, or should it work, just my problem might be something else ?

Thanks.
 

JMCx4

Censorship is the Sincerest Form of Flattery
Sep 3, 2017
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St. Louis, MO
If by "the middle and white end are a bit bigger" you mean they are longer than the plug you are replacing, those dimensions could vary by manufacturer & shouldn't matter as long as you can still attach the plug wire securely. More important dimensions are the thread outer diameter (which - along with thread pitch - must match the original to be able to screw the new plug in the engine receptacle) and the length of the threaded portion (which will determine the position of the spark gap inside the engine). I would recommend consulting your mower model's manual (on-line or received with the mower) to make sure you have a proper replacement spark plug before installing it. Misfires are one thing, but mismatched threads could result in a really bad day for you & your mower.
 
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Winger98

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Feb 27, 2002
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I'm betting on the "cheapest part first" theory. Though nothing's cheap any more.

Maybe. I was wondering if they were gunked up or something, if the thing had been blowing smoke, something to give us a better idea of what's all going on. I haven't seen many spark plugs go from fine to junk over night and for whatevers trying to use it to spark just up and die.

As for parts, it depends. I was looking at rebuilding the carb on my old push mower. A kit with all of the seals and what not is like $10. For $20 I can just buy a new carb and it'll come with a new air filter, a new fuel filter, some fuel line, etc. Really, if you're just a little bit handy and can remember how it goes back together, I'm thinking you could replace a bunch of the parts on a push mower without too much of a hassle and it beats throwing down the $300+ for a new one.
 
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TD Charlie

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Sep 10, 2007
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Maybe. I was wondering if they were gunked up or something, if the thing had been blowing smoke, something to give us a better idea of what's all going on. I haven't seen many spark plugs go from fine to junk over night and for whatevers trying to use it to spark just up and die.

As for parts, it depends. I was looking at rebuilding the carb on my old push mower. A kit with all of the seals and what not is like $10. For $20 I can just buy a new carb and it'll come with a new air filter, a new fuel filter, some fuel line, etc. Really, if you're just a little bit handy and can remember how it goes back together, I'm thinking you could replace a bunch of the parts on a push mower without too much of a hassle and it beats throwing down the $300+ for a new one.

Couple years ago I pulled the carb off an old push mower I got for free, cleaned it out, adjusted the spring to make it tighter on one of the butterfly valves, and it ran perfectly. Zero dollars. Zero experience. Took a couple hours maybe, most of that time spent getting the spring tension juuuust right so it didn't run too fast, but didn't stall out.

You're right, they really aren't that complex and are fairly inexpensive. I rather enjoyed taking it apart actually.
 
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HansonBro

Registered User
May 3, 2006
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Couple years ago I pulled the carb off an old push mower I got for free, cleaned it out, adjusted the spring to make it tighter on one of the butterfly valves, and it ran perfectly. Zero dollars. Zero experience. Took a couple hours maybe, most of that time spent getting the spring tension juuuust right so it didn't run too fast, but didn't stall out.

You're right, they really aren't that complex and are fairly inexpensive. I rather enjoyed taking it apart actually.
I think we're all bored and want something to take apart lol.

As per the OP, sometimes a quick job with some sandpaper can revive a fouled plug. Also if you are using last years gas, you can add methyl hydrate to clean up all the varnish in the system. I find my old boat motor needs a bit of that in the spring every year, then runs fine
 

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