P.S......does anyone have a method for working out exactly where to drill the hole for the pin? (my handle bars have a mess I made of several holes under the R.H. switch block, none of them in the ideal location!)
This job is a pain and I have found that some suppliers now have pre drilled bars available. They cost a bit more, but really worth it!
I had this challenge with the clip on bars for my Rickman CR. Looking through my scrap spares, I found two old switches (left and right) with no locator pins. They are also missing most of the guts, so I removed the internals. First I drilled the pin holes, right through the switch. Mount these to your new bars (mirror and levers mocked in). When totally satisfied with the location and angle, use the switch base as you drill guide.
Lay a piece of wide masking tape over you old bar holes. Trim out the pin and wiring holes. Transfer the tape to the new bar and line up on the pin hole. Start drilling and grinding with a Dremel to make the slot....