Honda CX 500 Forum banner

Bottom of Spark Plug Cap

4K views 67 replies 15 participants last post by  nolimitz 
#1 ·
After testing all the components of a cap and it still testing bad, I cut it open and found this at the bottom:

Electronic device Technology Electronics

It took considerable grinding with a dremel tool to clean it up to a point where I could get a reading:
Hardware accessory

Electronic device Technology Electronics Wire Measuring instrument

Electronics Electronic device Technology Wire Hand

I have about 10 of these old caps. Most tested bad even after I cleaned them up and the components tested good. I used to think the problem was inside the elbow, but now I'm thinking its at the bottom of the cap as shown in the picture. I'm going to try soaking the others in a de-ruster and see if I can get them to work. And I apologize for posting a picture of a rusty spark plug cap right behind Mike's fine looking valve covers.
 
See less See more
5
#8 ·
Maybe , if they age and look like that inside , I should also invest in a brand new original pair from DSS UK while on the quest for lower , more efficient fuel consumption ! :D
 
#9 ·
I've had good results cleaning inside spark plug caps by spraying in some contact cleaner and stuffing a bit of Scotchbrite in and rotating it a bunch of times with the tip of a small screwdriver. Sometimes it takes a few tries but it usually removes enough that you can get contact again.

But yes, new plugs are often a better option if you can get them...
 
#12 ·
I've been trying to clean my plug caps and have found that good tested caps at 5K ohms test bad after I take them apart and it's difficult to get them clean enough to test good again. It's hard to see to the bottom of the cap but I agree the problem is the bottom of the recess where the spring sits.

I can't determine what the material is. I suspect aluminum, but possibly brass. RVP3s photos give a good view but the material is unclear. Mine look more like aluminum, but his have a gold look like brass.

I'm going to try a combination of polishing with some sort of abrasive and perhaps a chemical like vinegar.

I know that replacements are available at a cost, but apparently they can't be dismantled like the originals and it looks like a simple fix once a good technique is found.
 
#17 ·
That's what I'm aiming for. I won't use vinegar for now for fear of causing increased corrosion. I assume you cut a very small piece of Scotchbrite that will get jammed to the bottom and then rotated with a long small screwdriver. How difficult is it to then remove the Scotchbrite? Will a blast of compressed air blow it out?
 
#15 ·
One thing that nothing will fix is where the brass ribbon that runs through the right angle has corroded through.

I have had a number now {I've cleaned up lots of these things from spares} where you can see the bright shiny metal at the bottom but there is still zero continuity through the right angle.

Test tube Electronic cigarette Medical equipment Tobacco Metal
 
#16 ·
Yeah, I had a few caps in the stuff I was selling cheap a few years ago and someone contacted me about them and asked me to test them first. They were all bad. I had never seen that before so I spent a bunch of time trying to clean them and making sure my meter and leads didn't have a problem. I have no doubt now that it does happen.
 
#19 ·
I use a straightened out paper clip with about 1.5-2mm bent a bit over 90 deg. to pull the little piece of Scotchbrite out. A blast of contact cleaner right before assembly will flush out any crumbs that break off and don't pull out with the rest of the piece.
I also clean the contact surfaces of the other parts (spring, resistor &c) with Scotchbrite & contact cleaner until they are shiny.
 
#20 ·
Exactly what I did with my plug caps to cure a major breakdown at 5000 rpm. Cleaned every component, cap bottom, spring and resistor until full continuity was established.
That plus new spark plugs completely restored the ignition system.
 
#22 ·
I was able to remove most of the scouring piece with a 4" #8 wood screw. I followed with WD40 and compressed air. Resistance is restored to 4.75K and 5.10K. Hopefully the WD40 will leave a protective film. When I looked on David Silver Spares for CX650E and GL650i I didn't see any listing for plug caps. They are listed for the CX500 which I expect are the same. Genuine NGK caps are $31.83 USD and aftermarket are $8.50. I'm glad my originals are still good but it's reassuring that replacements are available.
 
#23 · (Edited)
The GL plug caps are longer to fit the 'euro' type valve covers used on the GLs.

Ditto the mounting bolts.

A week or so back I had to make a mounting bolt by cutting and shutting 2 500 bolts as I found one of the bikes here to have one short bolt from an earlier model.

EDIT - I just went out to the shed to try to verify the difference in plug cap length. Simply, I can't.

I have two bikes here with the later valve covers. One has some sort of generic plug boots and the other is running coilovers so I don't have the caps from the later bikes to compare.

What I can say is that the 500 cap I tried fit the cover and engaged to the plug. It has the round 500 seal though. I don't know if the square 650 type seal would add any further requirement for height.
 
#24 ·
I've used the same caps with both covers. AFAIK they are the same except for the dust seal.

WD40 will leave a coating but it isn't what I'd call "protective". When the solvent evaporates a sticky residue is left. You might get away with it inside the spark plug cap but in switches, locks &c it attracts dirt and turns into a gummy mess.
That's why I specifically said to use electrical contact cleaner.
 
#25 ·
I'm not sure how people think WD40 is the end all be all magic fluid? It has its place but seems to be misused a lot. :ROFLMAO:

Cartoon Font Musical instrument Sharing Art
 
  • Like
Reactions: ss tuff
#26 ·
Is David Silvers a website to look at new ones?

can someone explain how to separate the boot from the ht wire itself. Thank you
 
#33 ·
Can someone tell me how to test the ohms using a multimeter I know the spec is 5000k one probe is on the screw in the right? Where would the other one go?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top