Hi ;
The tail light on my 1942 wm20 works when I turn on low beam but not on high beam. The brake light ( brighter ) works on both. Any suggestions to what may be the problem .?

Was it previously OK ? Does it have a four-position switch with 'T' taillight position ? If so, the tail should be receiving power regardless of what the headlamp is doing.

How is the brake lamp switch wired ? They didn't have one originally, of course. Has someone fitted a resistor system to use a single wire ?

What is the headlamp main beam rated at ?

The four position WD switch has the brass "butterfly" flappers which are wired in from number 3 to number 7. This enables the tail light to remain on through all position T. L. H. Ron

email (option): ronpier@talk21.com

Thanks for the information
It is on a bike I have repaired ( was told it ran before I bought it- had a seized motor , clutch was worn out etc.) I have rebuilt it. I put a brake wire/ switch on - works fine. I followed the wiring diagram I have , will make sure it is the same as this one. Last thing to do before registration.

The headlight I got only has off, L and H.

Were you using a civilian or WD wiring diagram ? If you have run the wiring for the WD switch then it won't be correct. On the non-WD switch with no facility for stand-alone tail, the rear lamp wiring runs to position '5' rather than position '1'