metric sparkplugs??

Page 1 of 2  

It seems to me that all the screws and bolts on my Japanese motorcycle are metric, except the sparkplugs.
AFAICT, neither the threads nor the socket required for the sparkplugs used in my Honda are metric. Is that so, and how did it happen?
If you are inclined to email me for some reason, remove NOPSAM :-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
mm wrote:

Huh? I though ALL sparkplugs were metric - a residual from the days (~1900) when the ONLY sparkplugs a U.S. engine maker could get came from Europe.
Are you saying we are slowly converting Asia to the Imperial System?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Well maybe the threads *are* all metric. I wanted to get a nut that would go on a sparkplug, to make a spark tester, and none of the English nuts fit. OTOH, I tried all the metric nuts and none of them fit either. OT3H, they didn't have nuts in all possible metric sizes. I think HD skipped from 12mm straight to 15mm, so maybe 14 would fit.

But even if the threads are metric, don't spark plug sockets come in 13/16 for the big ones, and other English sizes for the smaller ones?
Somewhere I have a set of metric sockets complete with extensions and spark plug socket, and I've been looking for them ever since I got my motorcycle. CAn't find them, so I don't know how the spark plug socket is labeled. (I've been using a bunch of metric sockets gathered from junk boxes along the way.)

Yes, that's why GWBush is in Viet Nam. He's promoting the inch, the foot, the pound, and most of all, the caliber.
If you are inclined to email me for some reason, remove NOPSAM :-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Get a spark plug heli-coil thread repair kit then drill, tap and thread insert whatever you want to.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
mm wrote:

I believe almost all sparkplugs are either 14mm or 18mm thread.

13/16 or 5/8. But I believe that the actual size of the hexes is the next smallest mm size; they're just close enough to make no never mind.
nate

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Honda frequently use 10 & 12mm plugs for mopeds and lightweight models.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ian field wrote:

OK, how about "almost all *automotive* sparkplugs." I wasn't thinking of small equipment applications and don't really know much about them for that matter. IME the VAST majority of spark plugs are a standard 14mm thread although now you're going to ask me what the pitch is and I don't know :)
nate
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Somewhere I have a really small spark plug that I drilled the HT stub so it could be used as a key fob ornament, not sure what size it is but its really tiny - its for a Honda portable generator.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ian field wrote:

They make even smaller ones, tiny really, for model airplanes.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The only ones I've seen myself are glowplugs which have a tiny coil of wire up the end which can be heated with a LV battery for starting, after which the combustion itself keeps it hot.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ian field wrote:

I had an original spark plug for old ignition engines (model airplane) sold it on e-bay for 7-8 dollars.
The glow plugs you are talking about are actually kept glowing by the catalytic reaction between the platinum, the alcohol in the fuel and combustion chamber pressures, not the heat of the ignition cycle itself. O.K. I'll remove my nerd hat now.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
mm wrote:

The two most commonly encountered spark plug thread sizes are:
M14 x 1.25
and
M18 x1.5
Someone with a lathe having metric screw thread capability could make you a nut pretty easily.
Or maybe you could find a junk cylinder head and bandsaw out the plug hole area?
*********** Trivia follows:
Some early US spark plugs used tapered pipe threads like this one I've had kicking around for years:
http://home.comcast.net/~jwisnia18/temp/plug.jpg
It disassembled for cleaning and had dual outer electrodes and a knurled nut for connecting the high voltage lead. A copper gasket sealed the ceramic to the lower body.
Mine is in pretty rough shape, the insulator was cracked when I got it and I epoxied it in place for show.
It is marked "Champion" on one side and "Maytag" on the other, so I imagine it was used in the engine of one of those gas powered clothes washing machines which were popular before rural electrification happened.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you need something to screw the sparkplug into, get an "anti-fouler" at your auto parts store. It is an extension with a fairly small hole to move the plug out of the combustion chamber.
Don Young
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Will I still be able to see the gap, to know if it is sparking?
If so, that sounds good. Thanks.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You may have to drill the hole larger or cut the male threaded end off. Take a look at one and you can judge.
Actually, you can get a big alligator clip and wire and/or solder it to the spark plug to do what you want better. You can even connect two clips together, hold the plug in one, and clip the other to the engine.
Don Young
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I don't know about the newer cars, but about 20 years ago when I was going to change the plugs in my first Datsun I stopped in the local Advance Or Autozone store to get some plugs and a socket. I had a good collection of American tools but nothing metric at the time. Told the guy in the store I needed a socket for the plugs and thought it would be metric. He did not know. We took some metric wrenches and matched them to the plug. They did not fit,but when I put one inthe American wrenches, they did. Turned out I had the plug socket for them all the time. Talked with a mechanic later and he told me at that time all the plugs he changed were the American type. I don't remember about the threads.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 17 Nov 2006 17:36:48 GMT, "Ralph Mowery"

I think now I remember that even American plugs have metric threads, like others have said. (It's just that HD didn't have 14mm nuts)
But we agree that they take English spark plug sockets, at least in the US. Don't know about Japan.

If you are inclined to email me for some reason, remove NOPSAM :-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
mm wrote:

Why not just get a "regular" spark plug and screw it into a "regular" nut? It's just for testing spark right? Or is this tester to test the plug itself?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Actually, I wasnt' using the plug from the motorcycle. I leave them alone. I had a plug from an American car.

Yes, I have some sort of tester that cost a dollar or two on sale at Harbor Freight, but it didn't work here because it anticipates a splug with the rounded nut on the end, and these plugs just have the screw.
And I thought of soldering an alligator clip to this spare plug, but that would be hard because the plug is like a heat sink, and bolting on a wire and having the alligator clip at the end of a short wire seemed more versatile.

No.
The good news is that after disassembling my dual coil/condensor package for the Honda CB450, and reassembling, now my right coil also has spark, if anything, better than the left side.
This is especially good since of the coils I bought via Ebay, only the right side seems to work.
So I found the 3/4" very narrow crack in my coil, probably caused by my leaving the ignition on for 2 and half hours, and I filled it as best I could with black GE silicone, and after that dried, I wrapped it several times with silicon tape. That's the stuff -- hard to find --one stretches and it grabs when you let go, and after a few days turns to one glob of rubber. The best tape I've ever seen. So I think, not sure, my coils will be all right for a couple years or more, and if not I'll buy replacements then.
Thanks to you and everyone who enlightened me about spark plug sizes.
If you are inclined to email me for some reason, remove NOPSAM :-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I suppose the more interesting question is in Japan, if the spark plugs are the same, are the sockets the same. Do they have the same standard size rachets or are the rachets themselves metric?
mm wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.