no sparky

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Aug 11, 2008
hello Im trying to get a 71 commando 750 started, wires were hanging off of the ignition switch. Does anyone have a photo as to which wires go to which location on the back of the ignition switch. Im trying to get power to the points.
Personally, I would want to try to identify the switch terminals, rather than rely on a photo?

How many terminals are there on the switch?

How many key positions are there?

Are the switch terminals numbered?

If the wires (and switch) are still original, then the power from the battery feeds to the switch along the Brown/Blue wire to the number 1 switch terminal.
White is the main circuit wire from switch terminal 2 to power the ignition, brake light, charge warning light etc., so Brown/Blue to White connects across the switch (T1 to T2) with ignition "ON" which should be the second from last switch position when turning the key clockwise?
The Brown/Green lighting wire goes to switch T3, and will have a connection across the switch to the Brown/Blue at the last clockwise switch position -"Ignition and lights".
wow! very thorough , thank you. I'm going to write what i find down and report back in a bit. It seems all original union key and all. I'll find out the wire colors/positions also i see a couple of wires taped beside each other almost as id the should have a modern fuse plugged in. Those two wires are white with a red strip.
There's a White/Red wire shown on the wiring diagram (WR) which runs from the handlebar switch (that switch could be either on the L/H or R/H side as they are interchangeable?) and it appears to go as far as the multi-pin connector, but it has no corresponding wire coming from the other side of the connector, so is an 'extra' wire.

1971 wiring diagram: ... p/150.html
First off, thank you for helping me out with this. I do have power on the White wire with the ignition switched to the second to last clockwise position. But I still do not have any power or ground to the coils. I tracked the white wire up to the gas tank wire splice and i can't see any relation between the white wire to the ignition components. Maybe there is a switching position that the hand levers need to be in? I do not know , this is my first Norton and It has not started yet.

So my problem is back tracking from the coils, with no power or ground at the coils, what would you suggest, do I have to have the hand switches in a certain position as well?
If you can get power as far as the white wire then that should supply the ignition coils via the kill switch and ballast resistor? Your '71 model would have had the ballast resistor and two 6 Volt coils originally.

If the wiring has been chopped about and spliced, then the fault could be anywhere?

But I suggest you use the wiring diagram in my previous post to follow the ignition circuit, as there should be a white wire running to the kill switch (press button) and from there a White/Yellow wire changes to a White/Blue wire, either at or before the ballast resistor?
The White/Blue then connects to both coil negative terminals, and each coil positive wire (Black/White and Black/Yellow) goes to one condenser and one points set?

Check that you also have a good ground connection running from the engine (cylinder head) to the wiring harness and back to the battery (Pos.) as the rubber Isolastic engine mountings make poor electrical conductors.
thank you for all of your help. I didn't notice the wire diagram link that you had sent until your mention of it in your last post. that helped out loads. Its a bad ballist resistor. Power in but no power out, upon removal found front windings of resistor corroded/missing. BINGO!. thanks again.
Earlier this year I had an engine problem and after serious troubleshooting I found out that the ballast resistor had an intermittent problem, at certain vibrations it worked and at other (actually low rpm's) it broke the circuit. Took it's time to figure that one out!

I bypassed the ballast resistor but kept the 6 V coils and it works great. There are others over here who have been running like this (no ballast resistor and 6 V coils) for years without any problems with the coils.

The Norton points cam closes and opens each breaker such that both sets aren't closed at the same time. It's possible to put the coils in series and parallel the two breakers (spark both cyls at the same time). But simply bypassing the ballast and using the 6V coils on 12V is asking for trouble. Coils will overheat and points will wear rapidly.
Yes, theoretically the 6 Volt coils would overheat but in practice it seems to work fine.
It was actually the local parts dealer that told me not to waste my money on a new ballast resistor, just by-pass it and run. I must say I was suspicious too but he has been running his bike in this configuration for over 10 years with no problem.

I guess time will tell who's right :D

After reading your posts on the subject I got even more suspicious about the dealers view on this and I phoned up our club's engine "guru" to discuss this.

Result? He fully agrees with your position on this subject :!:
In his opinion it is not a good practice to by-pass the ballast resistor and I was HIGHLY recommended to re-wire the system per your suggestion (or get a new ballast resistor).

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