Running lights elctrical problem?

[Blue2]

Hi all,
I've just bought a bike in the UK that was imported to here from Philadelphia US.
Now I have one or two electrical gremlins to sort out. it has a custom wiring harness that looks like it has been copied from posts here.

Gremlin Number one.
It won't start unless the light swich (non standard) is in the P for park position, this illuminates the rear tail light only, as the bike doesn't have a front pilot light, just main beam dip (low) and high beam.

Is this an American thing? do you have to have your tail light on by law? (it's an ex Philly bike) ie if you don't move the switch to P and put the tail light on you can't start the bike?
I'm working my way through the harness but haven't so far found a link between the P (park) circuit and the ignition??

My only guess is that with the lights in the OFF position, power to the Boyer Bransden ignition is somehow grounded. but I'm still searching for the link.

Other clues,

With the the bike running moving the light switch to the OFF position acts like a kill switch.

Removing the fuse from the lighting circuit has no effect on the ability of the light switch to kill the engine.

The bike has a perfectly working kill switch.

Any ideas greatfully recieved,
Dave.

 

[Detale]

Like you said its a custom wiring harness so who knows what the PO did or why. Maybe he had it as an anti theft switch of some kind. I know a few people who have done small switches somewhere on the bike that needed to be switched for the bike to start. You do need your tail light running I believe in most if not all states but that should come on when the bike starts. I'd say jump the circuit at the switch if you don't like it or re-wire to suit your liking. Check your local laws first and see what you need. Also what's a pilot light?

Edit: what year/model do you have. If you post the info it helps

 

[Blue2]

Hi Thanks,
a pilot light is what we call in the UK a side light. A little light in the headlight bowl that comes on at the first click, a front parking light. I'm not really sure that's a good description. The light that comes on before the headlight..
On my old 1977 Chevy pick up the front light that comes on with the first pull/click of the light switch.