1969 BSA A65L wiring

[johnsever]

Hi
I'm restoring a '69 A65 and am hoping someone can assist with identifying the three wires coming out of the alternator. They are Green with yellow stripe,Brown and Blue.  I cant find a wiring diagram showing these colours, so if someone can tell me how they connect to the rectifier I would be very grateful.
Thanks in advance
John

[L.A.B.]

I cant find a wiring diagram showing these colours,

Brown and blue are not the original stator wire colours so very likely someone has replaced at least two if not all three wires.

so if someone can tell me how they connect to the rectifier I would be very grateful.

Assuming the green/yellow is correct (which it may or may not be) and that the stator is a three-wire single-phase (RM19 and not a later 3-phase upgrade?)  then for a 12V electrical system, the green/yellow and one of the other two wires (normally green/black) are connected together and then connected to one AC terminal of the (presumably single-phase rectifier?) and the third wire (normally white/green) connected to the other rectifier AC terminal, however, as the colours are wrong then there's no way to identify which is which by the colours.   

Edit: I don't know exactly when the change occurred but I believe a 1969 A65L would normally have had a two-wire RM21 stator. 

[iansoady]

It sounds as though someone has used domestic 3 core flex which is a nasty habit as the wire is totally unsuitable. Have these wires been connected to stubs coming out of the alternator or have they been soldered direct? Probably at some stage there has been a wire / primary chain interface shredding the original wires.

As LAB says by 1969 it would have been a 2 wire alternator with Zener diode voltage control.

[johnsever]

Thanks for the replies. I cant see if the wires have been connected to the stubs of the alternator, and as the motor has just been re-built I'm reluctant to pull things apart to look inside, but that seems to be the only option. 

[iansoady]

You could use a multimeter set on ohm range for a rough check - it should be infinite resistance between any of the wires and earth, and around 1 -3 ohms between any pair of wires. Al Osborne has a good page on these (pdf download at www.aoservices.co.uk/info/ALTERNATOR_COLOURS.pdf)

[R]

It sounds as though someone has used domestic 3 core flex which is a nasty habit as the wire is totally unsuitable.

Why would that be ?

I know the copper content in domestic wire has been reducing over the years.
And the copper itself is purer than its ever been.
Does that affect 6v/12v operation much though ?

[iansoady]

Vehicle wiring has to withstand higher temperatures (possible ISO 6722) and also contamination by oil, fule etc as well as vibration. None of these affect household wiring.

As a side issue, people are often advised to use trailer cable for rewiring old British bikes. This is OK as long as you create a wiring diagram with the new colours otherwise a new owner will be driven to madness. I know I've been there....

Thinwall automotive cable in the correct colours is cheap enough and does a far better job.

[Rex]

Modern Thinwall cabling from someone like VWP is good stuff and I've got a few reels in the most common colours and the two most common sizes for bikes.
That said, I doubt it's made (or sold) to any different ISO spec than any other available similar cable whether intended for bikes or not. I don't make a habit of using domestic flex on bikes, but it's better quality than the stuff used on many (especially Jap)  cheaper bikes.
Strip it out of the outer insulation first though....nothing worse than seeing this or trailer cable being used on a bike.