Bsa B40 ignition & indicators

[AlanS]

Hi,

I have a repatriated 1964 B40 that after some issues is now road going. It is a long time since I last rode a classic bike, especially one without indicators and I found the experience somewhat exciting as most drivers have no understanding of handsignals or of slowish bikes, so I decided to fit indicators.
To get to the gist of the posting, I found that the lights, horn etc. all still work with the ignition key switched off (horizontal) so I have fitted a discreet key operated on/off switch accessed just under the seat, the switch is inline on the negative feed wire from the battery.
Everything works fine but I thought that by turning this switch off it would switch off the new indicators,lights etc. and the ignition. It turns everything off but the ignition.
Can someone clarify this please as I thought the ignition worked via the negative battery feed, a secondary point I found is that the bike starts better in the "emergency" switch position than the on (clockwise) position.
Regards
AlanS

[berniej]

Hi Alan,

I would have expected your isolator switch to cut the ignition if you were running in the regular 'I' position as in this position the coil is fed from the battery. However, in the 'E' position the coil is fed directly from one of the alternator coils. This is to allow starting with a flat (or no) battery so your isolator won't be able to cut the ignition in that position.

If the bike starts/runs better in the emergency position that suggests that the battery may be a bit flat or the main charging circuits not functioning well.

Cheers,
Bernie

[AlanS]

Hi Bernie,

You have confirmed what I had thought about the ignition needing the battery in-circuit but when I turned the new switch off the bike kept running until I turned it off at the ignition switch (it was in the clockwise/on position)
I checked the wires from the alternator to the ignition switch as I thought some may have been incorrectly connected but according to the wiring diagram they were all attached to the correct switch terminals. I did check the battery and it seemed to be charged OK, disconnected it measured 6+ volts.

I am better with spanners than electrics but will do further investigation on the battery condition and charging

Thanks for your advice
Alan

[berniej]

Hmm, I've heard many complaints about Lucas and Wipac electrics - although I think most have been about the bike not starting - not about it not stopping 

If your ignition switch is in the 'I' position and the bike continues to run with the battery completely isolated then it must be the alternator providing the voltage directly to the coil. I didn't think it was meant to work like that but will check the circuit diagrams in the Rupert book. Of course many of our bikes have had modifications to the original wiring. I'm planning to convert my B40 to 12V -ve earth as part of the restoration but that's another story!

Cheers,
Bernie