unclear function of switch at KH

[MartinL]

My KH and I are just getting to know each other. I know quite a bit about BMW boxers, but I have to realise that I have a lot to learn with my Ariel.
According to the AOMCC certificate, my KH 500 Twin was built in 1954, but the lists of frame numbers refer to it as a 1955 model. So probably built between September 1954 and December 1954. Unfortunately, an exact date was not given with the certificate. The machine was built for export to Belgium.
When removing the tank today, I noticed a strange switch that apparently goes directly to the magneto. Can anyone tell me what the function of the pressure switch is?
I can't find the switch or the cable connection in the wiring diagram from 1953 that I have.
Martin

[Chris Sealy]

It will be an, engine stop, or, kill switch. Assuming it is connected to a terminal on the rear cover of the magneto. It works by shorting the contact breaker points, thus preventing the magneto from producing the high voltage necessary for sparks.

[MartinL]

Thank you Chris. Do you know if this can be standard equipment or a modification by an owner?
I only have a wiring diagram from 1953 where it is not mentioned.

[will_curry]

Looking at the user guide in the members' only document repository - page 6:

http://www.arielownersmcc.com/members_o ... uideKH.pdf

It seems that the kill button was incorporated into the end of the magneto. Having said that,
my 1955 has a kill button on the handlebar, just like the horn button which I occasionally sound
instead of stopping the engine.

[nevhunter]

Don't we all? THAT sort of kilk switch just creates more possibilities of ignition glitches. I think I'd ditch it for the cover of magneto button. Hasn't it got The choke direct on the carb also?.Nev

[MartinL]

Thanks. Found it in the handbook where the switch is mentioned. Unfortunately, until now I can’t find a reliable wiring diagram of 54/55 KH. I guess I have to draw my own while disassemble the KH.

[paul.jameson]

What you have is the absolutely standard kill switch for the magneto. The easiest mount for it is a Z shaped bracket 6434-55, available from Drags which goes under the rear left handlebar clamp nut. I can send you a photo of this on my KHA if needs be.
The wiring diagram is the same as that for the singles, except for the magneto kill switch and the fact that you have 2 HT leads. But the wiring loom is different because the dynamo is in front of the engine on the KH instead of behind it as on the singles. I have used Draganfly wiring looms for both my KH and KHA. These are good, but the wiring colours don't match the diagram too well. No problem if you are familiar with the wiring diagram (which is actually very simple) but can be confusing if you are not.

[David Smith]

Strangely I have just got the parts to fit a kill switch to my KH in order to do some accurate plug chops!

[MartinL]

What you have is the absolutely standard kill switch for the magneto. The easiest mount for it is a Z shaped bracket 6434-55, available from Drags which goes under the rear left handlebar clamp nut. I can send you a photo of this on my KHA if needs be.
The wiring diagram is the same as that for the singles, except for the magneto kill switch and the fact that you have 2 HT leads. But the wiring loom is different because the dynamo is in front of the engine on the KH instead of behind it as on the singles. I have used Draganfly wiring looms for both my KH and KHA. These are good, but the wiring colours don't match the diagram too well. No problem if you are familiar with the wiring diagram (which is actually very simple) but can be confusing if you are not.

Thank you Paul.
With your description, I have an idea where this clip will be attached. There's no rush at all, but if you could take a photo at some point, I'd still be grateful. Apparently a previous owner changed the position of the Kill Switch at my KH.

Fits the length of the cables of Draganfly wiring looms well? Actually I plan to make up my own using the old cable loom as a template. Unfortunately, the Ariel wiring diagrams I found did not specify the diameters of the cables. But I will get this also from the old one.
On my R60/2 I renewed the wire loom last year. BMW is a bit more detailed in the manuals and of course I can understand German better than English

[paul.jameson]

Photo as promised.

I don't know where you are based but if in the UK I recommend AES in Tenbury Wells for wiring loom cables. Normally, I make my own, but I was in something of a rush to finish the KHA so bought a loom.