Spark plug wire: an interesting find

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Agreen

Agreen

Member
Feb 10, 2013
792
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Southeastern GA
So you've all heard that the supplied spark plug wire and boot are doo doo. Here's an interesting find that may ruffle some feathers!

I was cleaning out my garage this weekend when I found some leftover spark plug wires and boots. They are new parts that were going to go on a friend's Honda Shadow, but he sold the bike. Unfortunately, the first thing I noticed was that these are resistor boots. 5000 ohm boots are popular for reducing EMI noise. Not so good for weak little ignition systems like on the china bike kits.



But wait! What's this?



Does that flat head mean it comes apart? Why yes! Yes it does!



See the fuse-like thing between the spring and electrode? That's a ceramic 5k ohm resistor. A piece of metal the same size and shape should replace it just fine. In my case, it was a small bolt, cut down and filed appropriately. So I put it all back together and check resistance of the whole wire and get about 0.02 ohms. (The meter reads about that when you short the leads together anyway) So awesome! A free upgrade!!



Or, so I thought...
 
Agreen

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
After replacing the stock wire, I wanted to take a look at it. Here's a picture of it:



Looks different? Yeah, I thought so too. Take a closer look at the ends:





The end that goes in to the CDI is different from the one I had before. My last one was glued in. And it was a booger to get out. This one just plain unscrewed! The last one was also automotive style resistance lead, not stranded copper like this one. The other one I had used a plastic, low quality plug boot. This one's nice and rubbery, and makes a good seal.

Here's something else I noticed. See the boot end? See how different it looks from the NGK boot? The supplied boot is DESIGNED to work with the screw on cap on the spark plug. That's something that caught me off guard. I follow instructions pretty well, but I also have a bad habit for critical thinking. When I read that severe damage can occur if you don't remove the screw cap, I took it right off. I put the boot on and felt how loose it felt, it went right back on. It also gave me zero issue, I just wanted to try a new boot and wire.

Conclusion:

I gained nothing. The new NGK boot requires that the spark plug screw cap is removed. The resistance of the original boot was very close to the new NGK. The original boot feels rubbery and makes a good, weathertight seal. The new NGK boot is hard plastic, but has a nice seal at both ends.

So, somehow, I guess China is getting better with certain parts. I always heard the plug boot is garbage, but it seems that this one is of pretty decent quality.

Feathers ruffled?
 
Davezilla

Davezilla

New Member
Mar 15, 2014
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San Antonio Texas
Looks like you got one of the newer kits with the rubber boot and the automotive style spark plug clip that needs the little tip screwed onto the spark plug so it'll snap into place... these are the good ones.
Then the older style stock boots are similar to that NGK boot you got, but of far less quality. The NGK boot comes with a resistor to help supress the radio interference that can mess with other electronics like the ECU. Taking out the resistor and putting in a metal slug would be the right thing to do before installing onto a CG engine, but it's still going to have some little amount of resistance or maybe a poor contact somewhere in the boot. These ignition systems aren't very strong so even a few ohms of resistance can be the difference between a fire or a miss during acceleration where cylinder pressures are at their highest.
Why one worked better than the other after you removed the resistor and replaced with a metal slug I'm not sure, but it should have worked just as well. It could be just a thin layer of oxide on the brass parts from sitting for so long or a bad contact on the wire where it was screwed in but without it in front of me it's hard to tell. I did have a similar problem with my Sportster not wanting to crank over and all it was was a very thin layer of oxide on the brass lug on the ground wire... it looked normal but after cleaning it with emery cloth until the brass was really bright and putting the terminal back on it fired right up when before cleaning it all I got was about 1/2 turn then the dreaded click click click sound and no start.
You could try taking it apart again and cleaning all the metal parts that make electrical contact and trying again, but you also got the better type spark plug boot already...
 
Agreen

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
I think you may have read it wrong. What i found was that although they're different style boots, they are equally as good. I'm staying with the NGK boot, and I'm having no trouble with it. It still read close to 0 ohms after a test ride.

So the blanket statement about all CG boots being trash is no longer applicable.
 
Agreen

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
I'm definitely keeping the original one as a spare, but I like how the NGK boot is so much taller. It cleans it up a little by getting the wire along the frame. So for now the new boot and wire stays.

Oh, and the supplied spark plugs are still junk. So change it out asap!
 
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