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GL1100 Engine2

An online source dedicated to Honda's amazing four cylinder Goldwings!

Plug Cap Corrosion

This tip is mainly for the owners of the GL1000.

The GL1100/1200 run electronic ignition which has a far greater capacity to overcome the double resistance mentioned. But the corrosion and the cleaning still apply to these bikes too.


Got a mysterious misfire? Try checking out the INSIDE of your plug caps!


I had chased a misfire fire a while. Realising that there were resistor plugs fitted as well as resistor caps, unnecessary and undesirable, I decided to remove the cap resistors.


This is easily done. Look inside the cap and you will see that the brass clip-on part is slotted for a screwdriver. Undo this and remove the small resistor and the spring.

You will need to make up four lengths of brass rod, 4mm diameter and 31mm long.

Slip these inside the caps and replace the screwed in part.

Check the continuity of the cap with a meter from the clip-on part to the HT lead screw to make sure the brass rod is contacting properly.


Before I did this, I checked out the resistance from plug cap to plug cap. This was where it got interesting. The coil supplying the two cylinders that were firing gave a reading fairly close to what would be expected.

But the reading through the other one was in the region of 38k ohms!!


On a continuity check, there was NO continuity!


But this set had been firing, albeit with a stumble. Removing the caps from the HT leads, the reading through the coil was fine so the problem had to be in the caps. Sure enough, with the tiny current from the meter,  there was no continuity reading in either of them. So, although the high voltage current was managing to get through somehow, it was having some difficulty.


Curious, I checked out some other caps and finding a broken one with the same problem, I broke it open to show you.


The inside where the spring sat was completely blackened with corrosion; the underside of the clip-on part likewise. These should be a nice bright brass colour!


A quick clean up on the originals and the brass rods in place, the resistance reading was now 12k ohms. Much better!




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J G Evans

HT cap corrosion (Small)
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