G2 wiring issues - 1959 bike

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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G2 wiring issues - 1959 bike

Postby craigcc » Sat Dec 29, 2018 1:45 pm

Hi all,
Some advice needed please.

I'm near the end of a restoration of a 1959 G2. A nice project on a bike which I feel is under appreciated in the classic world - aside from the problematical FB forks of course! Anyway, the bike is looking smart and running again, but I'm getting no charge from the alternator.

The original Wipac alternator and rectifier were fried, so I replaced these with a new Lucas three wire 6v alternator and a solid state rectifier. Sorting out the wiring for this has been a bit of an issue, as wire colours in the loom don't always match any of the diagrams, so I had to trace where each one went, particularly inside the headlamp switches (for example, the light green wire that connects to the alternator in the diagrams is actually white in my loom).

On the original set up, an orange wire and a yellow wire from the loom were connected directly to two of the three wires on the alternator, but the various wiring diagrams for different models show the yellow wire as only connecting the ignition switch to the light switch. The only diagram which shows the yellow wire connecting to the alternator (via joining to the light green alternator lead and not having its own dedicated alternator feed) is for the 250 scrambler without a lighting set - not my bike.

Also, the white wire was connected only to the old rectifier on the previous set up on my bike.

So my current set up is White (light green) to the ignition switch, via the rectifier (as per various wiring diagrams).
Orange direct to the ignition switch (also as per diagrams)
Third lead from alternator to the rectifier (again ref diagrams)
Rectifier positive to earth
Rectifier negative to a four way bullet connector which feeds the battery and the mail wiring loom

Yellow under this set up is currently rendered redundant, though it connects the ignition switch to the light switch at the headlamp end, as per the diagrams.

Obviously, I'm doing something very wrong as no charge to the battery. All the rest of the electrics work OK. Puzzled. Is there a specific wiring setup for the 1959 bikes for which no diagram now exists?

Any advice? Also, any thoughts on which colour wire from the Lucas alternator should go to which colour wire on the Wipac loom. Wouldn't be surprised if I'm doing something wrong here as well.

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Re: G2 wiring issues - 1959 bike

Postby craigcc » Sat Dec 29, 2018 1:50 pm

I should clarify:

So my current set up in terms of alternator wire connections is:

White (light green in the diagrams) from alternator to the ignition switch, via the rectifier (as per various wiring diagrams).
Orange direct from alternator to the ignition switch (also as per diagrams)
Third lead from alternator to the rectifier (again ref diagrams)
Rectifier positive to earth
Rectifier negative to a four way bullet connector which feeds the battery and the main wiring loom

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Re: G2 wiring issues - 1959 bike

Postby clanger9 » Sat Dec 29, 2018 4:12 pm

Given that you've got a non-standard setup, I think you'll need to do more than just match up the right colour wires.

The original Wipac system uses a cheap 'n' nasty system using a switched resistor to regulate the charging rate. It assumes the alternator has a specific output. I'm not convinced that it will work properly if you have changed the alternator to a Lucas unit, as this will presumably have a different output. You might be better off fitting an electronic regulator.

The Wipac manual has a really clear explanation of how to test and diagnose the charging system components. I'd recommend following that first to check that everything is working (from page 100 onwards).
http://archives.jampot.dk/technical/Ele ... -60ies.pdf

After that, you can trace each connection according to the wiring diagram. Here is a link to the 1959 diagram (last page):
http://archives.jampot.dk/technical/Ele ... _Wipac.pdf
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: G2 wiring issues - 1959 bike

Postby Janet » Sat Dec 29, 2018 9:24 pm

craigcc wrote:Any advice? Also, any thoughts on which colour wire from the Lucas alternator should go to which colour wire on the Wipac loom. Wouldn't be surprised if I'm doing something wrong here as well.
I am somewhat confused about what wires you've got going to where because your colours aren't standard. Perhaps you could copy a diagram of a standard loom and change the colours to what you have. Then you can tick off each wire as you check it off as correct.

Regarding you Lucas alternator, I have a single phase, 6v one with three wires coming from it, i.e. green/white, green/yellow and green/black. It may be different for other Lucas stators but It has six coils in two sets. Unlike the Wipac which has two sets of 3, my Lucas one has 2 and 4 coils. The g/w is common to both sets, and would replace white from the Wipac alternator. Because the two sets of Wipac coils are identical, the light green and Orange wires are interchangeable, whereas on the Lucas, the g/b has two coils and gives low output, and the g/y with 4 coils gives high output. Whether or not it matters which way round they're connected will depend on the output of the alternator. If correctly wired up, both sets will kick in when it calls for a high output, such as when using emergency ignition, but on a low output version, having the two coils alone may be insufficient even for running with minimal draw off from the battery.
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Re: G2 wiring issues - 1959 bike

Postby Bernie.Jones » Mon Dec 31, 2018 2:42 pm

If you have a similar stator to Janet's, i.e. G/W, G/Y and G/B then you could test for AC output with an appropriate meter to check that you at least have some basic raw output from the alternator.

Disconnect all three alternator wires from the loom and connect your meter, set to AC ( or ~ ) voltage, between the G/W and G/B wires. Then repeat with it connected between G/W and G/Y. You should get a reading in both connections (with engine running that is!) probably in excess of 6V depending on revs.

If not then there's a basic problem with the alternator that need to be addressed first.

I'm actually doing the same thing with my G2 which came without a stator and am fitting one from a Triumph cub so will be making the same tests once the bike is together and running.

Cheers,
Bernie

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