There is no headlight relay. Is this a regular headlight or some kind of super-anti-kangaroo flame throwing headlight? What happens if you disconnect the headlight wire on the switch, start the bike, then run a jumper from the headlight wire directly to the battery +? Still miss on you or nothing? I'm thinking 989HRFB has it at the switch problem.

 

Somewhere there's a funky connection probably a small wire harness ground that loses connectivity when the light starts drawing amps in the system.

 

Good one Doc. No it's just a 55/60.
I've cleaned the earth terminals to no avail. With the H/L wired direct to battery and wire disconnected from B all was good. So it does point to the switch.
While I'm waiting for one I'll take the tanks off and service all the connections.
I don't ride much at roo o'clock (dusk till dawn) if I can help it. The rHonda ***** has the 55/130 anti roo light.
Thanks heaps for everyone's help.
Cheers

 

Could be built up resistance on the handlebar switch. I like to take them off every few years and do a real good cleaning with contact cleaner, then regrease them. You can eliminate most of those problems with a few micro relays and some wiring, the headlight will be much brighter too.

 

G'day Kowboy.
That gave me a thought. I recently put black handlebars on. Wondering if that could give an earthing problem.
I've tried a few of my usual suppliers for an ignition switch. None have stock and one said January for new stock. Might have to take a mortgage on the house for a genuine HD.
Another thought (I've done on my rHonda) is to run the + wire for the coil to a relay and give the coil full battery power. Might do the same for the H/L, then I could run a super-anti-kangaroo flame throwing headlight.
Cheers

 

G'day Fellas.
The new ignition switch arrived yesterday and installed last night. Seems to have fixed the problem. Now at revs with the head light on high the coil is getting full power 14.5v and at slow idle gets 13.2v. I might get a chance to road test tonight.
Still in lockdown so limited to a 5km radius from home. Getting dizzy riding round and round the block!
Cheers