This post describes the process I used to make a new cork lining for the ignition sensor (bean can) lid on my ’84 R100RS.
After removing the two retaining screws, the easiest way I found to remove the lid from the ignition sensor is to use channel-locks and gently pull away at opposite sides of the lid.
Inside the lid shows the original lining I assume is cork. It shows deterioration and distortion and appears saturated in an oily substance.
The lining fits into the lid which is dished about two millimeters and extends to the outer lip of the lid – apparently serving as a gasket.
Polling others with previous experience I learned that some ignition sensors were not lined – or found to be unlined when serviced. Tom Cutter of Rubber Chicken Racing Garage mentioned using a remnant of Snap-On tool box drawer lining material to make new linings when he does ignition sensor overhauls. No one I spoke with seems to know for sure why the lid has a lining.
I measured the thickness of the lining to be about 1/32″ – and found cork material of that thickness to be readily available (amazon.com) for a few dollars.
After failing to make a good tracing of the lining to make a new template, I decided to do it by photographing it and printing it to scale. Click this link to bring up the template I made.
To make the holes in the cork linking I used brass tubing to make two punches. I sharpened the tubing edge with a file to make clean punch. Because of the distortion of the old lining, there’s no way to know exactly how big to make the holes. So I simply took the lid to the hardware store and found brass tubes that seemed about right. Aluminum tubes would have worked just as well – but the store had brass. Only a couple of dollars.
Because cork and metal are dissimilar materials, I decided to use rubber cement to glue the lining into the lid. And when I removed the old lining, it left a residue that seemed like the original lining was attached with something similar.
Here’s the materials I used in making a new cork lining:
The paper template is a couple of millimeters too small because the lid is dished. To make the right size cork disk I traced the lid on the cork with a Sharpie – and then cut around the outer edge of the black line. That worked out to about the right size.
I then placed the paper template over the center of the disk, and used the brass tubes to punch holes in the proper places. It seemed to work best when I used the mallet to start the punch and then rotate the tube to finish cutting through the cork.
Removing the old lining was very easy – it scraped away easily with my fingers. I used my Dremel tool with a Scotch-Bright type attachment to clean away the residue and minor corrosion.
After cleaning the lid, I painted the cork and the lid with a thin layer of rubber cement using a small paint brush. I slowly formed the cork into the dished inner surface of the lid. Only a small amount at the outer edge required trimming.
Working slowly, the heat from my thumbs seemed to allow the cork to follow the surface of the lid with little difficulty.