Cleaning Spark Plugs

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550
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Wisconsin
I've got an aging, rich running, oil burning, fleet of small engines . . . mower, tiller, snow blower, etc. that carbons up plugs in a hurry. Scraping them isn't really effective. Grit blasting leaves them rough and full of, well, grit. Pyrolizing the carbon with a propane torch or in a self-cleaning oven works well but seems a bit drastic. Is there some sort of chemical, perhaps a lye solution, that would take off the carbon without harming the plugs? It seems a shame to throw them away after only a few actual hours of use. [ November 13, 2005, 08:11 PM: Message edited by: BigAl ]
 

BigAl

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Wisconsin
quote:
What's wrong with a wire brush?
1) It doesn't reach down very far along the center insulator, where the somewhat conductive carbon can rob spark energy. 2) As it does rub along the center insulator it leaves little visible trails of metal in the porcelain, which can lead to arcing and carbon tracking later. Since you can't see the spark plug in action, you won't be able to notice this, other than in misfiring or hard starting. I work with Ozone generating equipment, which operates at very high voltages, and has ceramic insulators almost like spark plugs. Little things like this become very obvious there. (Bzzzzzzzzzzzzzzzzt! . . . smoke.)
 

Kestas

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Luckily, I have access to a grit blaster. I rarely buy plugs anymore. Like you said, it's critical that the insulator stays clean.
 

Kestas

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Conversely, what's the harm in cleaning them to save some money, instead of replacing them? THe money I've saved over the decades has really added up! I replace when the center electrode erodes too much and gets near the insulator, somewhere between 50-100K. You may be right about the compression gasket design, but I've never noticed any problems develop from reuse. I believe the other design is just a ~45° taper seat.
 

BigAl

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Wisconsin
quote:
This question is just asking for it I know, but unless you have the $25 a piece factory OEM iridium style plugs, what's the harm in just replacing them, instead of cleaning them?
I wouldn't bother cleaning plugs in my car, but they last for years. These plugs are not eroded or worn in any way . . .they get fouled quickly in this old equipment. Like I said in my original post:
quote:
It seems a shame to throw them away after only a few actual hours of use
But if you don't mind wasting money and depleting resources by throwing stuff out that's practically new, then there's no reason not to just replace them. I could also buy botique oil and change it before it even gets dirty. I have never experienced a gasket problem from re-using plugs either. And even if I did, it's not like my rototiller is going to leave me stranded in the middle of nowhere. [ November 14, 2005, 02:19 PM: Message edited by: BigAl ]
 
Messages
1,241
Location
Glenshaw, PA
The point that I was trying to make is that given most small engine plugs take a buck or buck 49 in cost plug, why put the time and effort, plus the cleaning solution cost into cleaning and reusing the plugs? Not that I'm one for waste and abusing resources here, it just seems to me that even given the fewe hours of operation, cost vs time issue would be in favor of just replacing the plugs, instead of removing the old ones, cleaning them, regapping, the reinstalling them, and opposed to removing and replacing (most plugs these days do not need gapped, as they are pre-gapped from the factory. Only rarely did I see plugs come totally screwed up). And yes, I let my botique oil get dirty before replacing it...
 

BigAl

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A decent US made small engine plug costs about $2.50 at Autozone. The Chinese ones at Menards cost $1.89. They don't come pre-gapped, so removal, gapping, and reinstallation takes the same amount of time for a new one as a used one. What I have been doing is servicing my equipment in the spring, installing new or cleaned plugs, gathering up the used plugs, and putting them aside to put in the oven the next time it needs cleaning. They come out nicely de-carboned, but the plating on the metal is dull. It takes less time to pop them in the oven than a trip to the store, so I'm ahead there too. My old two-stroke pre-mixed outboard used pretty expensive oddball plugs. If I did a fair amount of fishing, I might foul a half a dozen plugs in a season. The oven trick saved me maybe $25 a year there. (Now I just use a canoe . . . and the paddle always starts on the first pull.) Currently, my newest piece of outdoor power equipment is from 1978, and with a little care each season, it all still runs very well. If I can save a few bucks each week one way or another, at the end of the year I have a nice wad of bills. I was just wondering if there was an even easier way to do it.
 
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1,241
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Glenshaw, PA
Now I see where you are coming from. How's about a long overnight soak in a fuel system cleaner, or maybe MMO? The only thing that would have me question your lye suggestion would be the corrosive factor on the plug materials themselves.
 

BigAl

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550
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Wisconsin
Lye will react violently with aluminum, but not with iron. Used carefully, it will remove the remains a siezed piston from a cast-iron cylinder bore without resorting to a machine shop. A couple of years ago, my wife left a stainless steel pot on the stove and the food burned on so badly that I couldn't pry it off with a putty knife. On a lark, I poured in some lye based crystal drain opener we had and added a little water to it. A half hour later the stuff rinsed right out. People use lye to strip chrome off of plastic. I don't know what it would do to the plating on a spark plug, or to the ceramic insulator. Carb cleaner does not work. Paint stripper doesn't do much. Lime-away did something, but not enough. Just trolling for suggestions . . . .
 
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Frankfort, Kentucky
I don't know if this is what you may be looking for, but I put a spark plug in a bit of acetone I was going to use to remove some tape residue and after 5 minutes there was a nice brown tint to the acetone. Might try an overnight soak in acetone if you are experimenting with it in your gas. I will be trying when I buy new plugs.
 
Messages
1,241
Location
Glenshaw, PA
This question is just asking for it I know, but unless you have the $25 a piece factory OEM iridium style plugs, what's the harm in just replacing them, instead of cleaning them? I was always under the impression that once torqued to specs, that gasket (if your plug has it, which mine do) was compression fitting, and that once compressed to spec, couldn't seal the same way again against the heads. I know that the other style (no gasket) would probably be OK now matter no many times they were removed. Am I misinformed?
 
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392
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Central Florida
I had posted a smiliar topic(same title) here I like the responses you are getting...I like the self cleaning oven idea. But other ideas and tips would be great too. And what about B-12, would that work???
 

Kestas

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The Motor City
Glass is a very good medium... less aggressive than sand. I've used glass in the portable, self-contained unit and in a cabinet. Both clean the plugs.
 

BigAl

Thread starter
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550
Location
Wisconsin
Some spark plugs still come with the little screw-on aluminum tip where the wire connects. If any of you are planning to try the self-cleaning oven trick, make sure you remove this part first. Otherwise it will just sort of disappear. I do have access to a glass bead blasting booth. Maybe I'll try it and see how it works.
 

Kestas

Staff member
Messages
13,946
Location
The Motor City
Once cleaned by grit blasting, I like to go over the threads with a wire wheel to make them smoother and easier to thread into the hole.
 
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