Headlamp resistor.

[tlc]

When I bought my `77 Z1000 it did not have the resistor in the headlamp circuit. It also had the original 40/45w headlamp. Despite this pathetic power output the wiring to the headlamp within the switch had warmed up sufficiently to melt the insulation. I understand that as a battery drops its voltage its amperage increases and this could have caused the problem, but having now converted to 55/60w I am keen to prevent this happening again.
I note from the wiring diagram that there is a .5 ohm resistor in the circuit but this confuses me somewhat. Surely using the VIR calculation that will allow a maximum of 72 watts. It also states that 20 watts is measured at the resistor. (Surely not ?) Is this another famous mistake ?
I may well be answering some of my own questions here but the headlight dims quite markedly when I apply the brakes. Could this be down to the fact I am still running the original charging system ? I note that there is a more modern combined regulator / rectifier unit. Does this cure the problem or am I being too fussy ?
The wiring on my bike is in excellent condition for its age and I can recognise shit wiring when I see it. I do not believe that wiring / earthing problems are affecting me in this case.
I will get a resistor if that will help but am confused by the markings in the diagram.
Sorry to go on but someone out there may have suffered similar ?

[Pigford]

Old Jap electrix are reknown for shite earths, and I would be tempted to run a dedicated earth just for the lights, direct to the battery or at least a good clean earth on the frame/engine especially as they dim when additional lights are coming on

[tlc]

Good idea Piggy !
But why is there a resistor in the circuit ?

[Big John]

Not sure if the resistor is actually a resistor wire.

[Rich]

I would expect that 30 year old wiring is knackered. The outer may look in good condition, but strip the insulation off the wires and look for effects that the copper has oxidised (black).
Even though the headlight left a lot to be desired when new I would check the voltage drop to the headlamp and see how many volts are actually coming through. As Piggy says dedicated and good earths do make a difference and are always worth putting in.
If you still have problems consider changing the headlight to a Xenon one, better light output for the same wattage.