DOes anyone have an opinion of whether, having one diode of a Lucas rectifier burned out, is enough to stop a bike from starting? I guess I will find out when I fit a new rectifier on Friday.
If it's shorted the system voltage to earth, then you won't get a spark, but then you would have blown the main battery fuse or smelt burning wires...
You could just fly-lead the battery to the coil terminal?
It's OK, I have a spare, modern rectifier which I can drop in on Friday when am at home. I am just working my way around the system. I had this bike running at one point, and now it has given up.
BTW, this is my no 1 bike. No 2 is still starting first kick. My aim is to get both bikes to running condition at the same time, but that is proving to be a challenge. Sod's law says that when I sort out No 1, No 2 will give up again.
Still, I am, at least, getting intensive training in caring for old bikes.
Re rectifier. Yes it probably is. Depending on how its failed - open circuit or short circuit you will either be getting intermittent power or a mix of AC and DC or a current drain to earth and burned out wires. None are very good.
It's always a good idea to have a fuse between the rectifier and the battery. It will protect the rectifier if the battery is connected the wrong way round and it will protect the battery and the wiring if the rectifier fails and shorts to ground