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Bigsieuk
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VBMWMO #8791
Joined: 02/27/2012
Posts: 100

Hello all,

I'm replacing the ignition switch and key barrel on my R12. I have the repair kit and new ignition 'board', does anyone have a diagram or picture of how it goes together?

Regards

John

Darryl.Richman
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VBMWMO #6285
Surf City, USA (Santa Cruz, CA)
Joined: 10/27/2006
Posts: 2185
Most of these ignition

Most of these ignition switches work the same way. The physical bits are a cap, a barrel, 2 ball bearings that fit into holes in the side of the barrel, two spring steel clips that clip around the barrel to hold the balls in place, a coil spring that goes around the barrel, and an insulator tip that goes inside the barrel. The whole arrangement is then pinned between the inside of the headlight shell and the circuit board.

The circuit board has four slots around its central hole, and there's a spacer that is spot welded to the inside of the headlight shell, which ends in 4 tabs that fit through these slots. The idea is that, while holding all of the pieces in place by compressing the board against the spring - without either bending the actual switch arm mounted to the underside of the board, or cracking the board - and holding it tightly against the spacer, with your third hand you bend or twist the tabs to lock the board in place.

I have done this with a couple C-clamps applied with much care. The tabs are problematic, too. With a few bends, they work harden and break off. I think it is the Barrington manual that describes how to re-anneal them (with the board off) so that they have a new life. If I recall correctly, one way is with a small torch; another is using an auto battery. In either case, the goal is to get them red hot and then let them cool down.

You should also be aware that there are two different boards for the R12, depending on whether you intend to run the battery/coil ignition (as was common on the civilian bikes, but is now extremely rare; you will have to have the Bosch RS generator, the one with the oblong points cover); or if you are running magneto ignition (as was present on all authority and war bikes, and is now almost the only way you see them; with the Bosch D2 magneto/generator ).

These two systems require different circuit boards. Externally, another difference is that the magneto bikes had no provision for a charge light; coil bikes had a charge light opposite the fuse holder next to the ignition key hole. My experience was that all of the repop stuff is for a battery/coil bike, but getting an RS generator is nearly impossible, as is getting it restored.

If you need a circuit board for a magneto bike, there are several sources, such as Vech at Bench Mark Works, that can supply you with a BMW repop /3 (early 1950s) circuit board. This will fit into place and work for your R12. It also has provision for a charge light, which you can hook up if your headlight shell has a hole for it and if your magneto has an electronic voltage regulator, which will have provision for the charge light wire. Then it is a matter of finding a suitable way of running another wire up to the headlight.

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VBMWMO Webmaster,--Darryl Richman
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Bigsieuk
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VBMWMO #8791
Joined: 02/27/2012
Posts: 100
Thanks

Thanks Darryl,

I found and old diagram which had the parts in some sort of order. As you would expect with R12's the ignition barrel and key weren't the original BMW type, so I thought I'd check on my other R12 to see how it looked. Surprise surprise it too isn't an original barrel/key!

My tan R12 has two lights either side of the ignition, but the ignition board has Russian letters on it. I bought a replacement from RRC. I've just managed to get the new board onto the prongs, all I need now is to order a repro key now and consider buying a second ignition board, barrel and key for my grey R12!

Fun and games as always.

Regards

John

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