Electrical puzzel

[Ohara]

My neighbour broke down in front of my house yesterday. He is riding a beautifully restored Norton Commando. It lost all power. I can usually find the cause for electrical troubles but this one has me scratching my head. Battery fully charged, turn key on and battery immediately drops voltage to as low as 4 volts. No electric start on this bike. Can’t find a short nothing is hot fuse is not blowing. Guessing a ground problem. But thought I would ask here as one of you fellows may have come across this before. It is a 1972 Commando.

 

[pidjones]

Lucas, Prince of darkness.

 

[Rednaxs60]

If the battery drops to 4 VDC - if all is well shouldn't drop below 11 Vdc but if so not much lower, the battery is most likely toast. Load test as well as a health check. A bad cell or cells can be the culprit even if the battery reads 12 VDC. Agree with Pidjones.

 

[Ohara]

Prince of darkness is correct... I got lucky and found the voltage regulator wire going to the battery was the culprit. A couple of things threw me, first it should not have a regulator also being a positive ground system. PO had upgraded to the voltage regulator eliminating the rectifier and heat sink zenter diode. Once I calmed down and started checking the wiring like any other bike as I said I got lucky. Who ever wired it up did a really good job. Looks like Ernest did it as it is nice and tidy. Thanks for the moral support.....I know this was not a Golding but I find most motorcycle enthusiasts like all brands of bikes, although we do have our favourites.

 

[joedrum]

Good deal