Hi, Can anyone help? I am rebuilding a 1982 xj750 seca and I'm trying to source a diode that fits in the headlight shell. It terminates to a six way connector but only has 4 wires. They are coloured:- Light blue on pin 1, nothing on pin 2, nothing on pin 3, white/blue wire to pin 4, white wire to pin 5 and black yellow wire to pin 6.  Looking at the wiring diagram in the Haynes manual the wires are different colours. (White/blue, Blue/yellow, Light Blue and White)

Can anyone explain what the diode actually does and where can I obtain one from?

Cheers and STAY SAFE

Have a look here https://www.cmsnl.com/yamaha-xj750r-seca-1982-c-usa_model8879/partslist/?filter_assembly_group=electrical#.YBA_juj7SUn

very simply, a diode is a bit like an electrical valve, it lets electricity flow one way and blocks it going the other way. stops damaging feedback to other electrical systems

Its the rectifier, takes ac from the generator feeding to the headlight, once the rectifier has made it into dc(of sorts) it goes to the battery and the rest of the bike.