How to fit electronic ignition

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Re: How to fit electronic ignition

Postby clanger9 » Wed Jan 23, 2019 11:44 am

Yep, there are loads of ways to do 12V! My guide is just the method I used.
Pick whichever one you prefer...
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: How to fit electronic ignition

Postby ChrisTheChippy » Wed Jan 23, 2019 11:01 pm

Yes there are loads of ways to achieve 12v unfortunately to someone like me grolly might as well be speaking Martian !
What I needed was a step by step guide with easy to follow instructions and I believe Paul has achieved that .
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Re: How to fit electronic ignition

Postby Groily » Thu Jan 24, 2019 7:36 am

Was just listing the common options for dada, Chris, in answer to his separate Q!
Step by step instructions for various ways of doing it are also set out on p 219 of James Smith's most excellent book 'Classic Motorcycle Electrics Manual' (worth every penny as GOLDSTAR implied), and Goffy's site is pretty clear too I reckon.

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Re: How to fit electronic ignition

Postby Martin.S » Fri Jan 25, 2019 3:19 pm

3 phase connected across the 2-phase feed. The diodes sort it all out (it’s just using 4 of ‘em instead of all 6).

Sorry Paul - could you please elaborate - I don't understand 2 phase? and 4 of what?
I can't find anything to suggest that the alternator is 3 phase.
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Re: How to fit electronic ignition

Postby ChrisTheChippy » Fri Jan 25, 2019 5:54 pm

Thanks grolly . At least I will have a back up plan when I get stuck !
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Re: How to fit electronic ignition

Postby clanger9 » Sat Jan 26, 2019 4:04 pm

Sorry, I should have been clearer. The alternator is 2-Phase. A 3-Phase regulator will work perfectly well with a 2-Phase input.
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: How to fit electronic ignition

Postby Martin.S » Wed Jan 30, 2019 5:49 pm

Hi Paul, I asked the question on the Norton forum and got a reply from Al Osborn(he who knows about these things). Wipac alternators are single phase and the correct way to do it is to join two of the alternator leads together and use a single phase Reg/rectifier. Although the way you have done it works it's not the best way to do it. Hope you don't mind me bringing this up 'cause your guides are much appreciated.
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Re: How to fit electronic ignition

Postby clanger9 » Wed Jan 30, 2019 6:27 pm

Absolutely, there is no problem with wiring the alternator into a single phase regulator (if you join the orange & light green leads). This is the usual way to do it.

However, there's no issue connecting the Wipac alternator directly to a three phase regulator either. The internal diodes in the rectifier pick up the AC from each of the two alternator legs (and you don't have to identify the right wires from the alternator, which can be difficult if the wiring colours aren't original...).

I'll update my guide to reflect this.
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: How to fit electronic ignition

Postby Groily » Fri Feb 01, 2019 4:03 pm

Like Martin, no wish to undermine so much good work here. But FWIW here's a simple schematic of a basic 12v set-up the more traditional way, which is designed to reduce the number of wires to a minimum for those not interested in following the 'book'.
It's what I use happily on my 2 alternator machines, and have done on a number of others. Have also used it on 6v ac systems with an A Reg 6 unit.
Switches vary between bikes, so no terminal numbers shown, but the main take-offs for head, front side and tail/speedo are usually easy to identify. Ign sw just needs to do On/Off basically. (Emergency position not catered for.)
This one is Neg earth, but apart from swapping the battery, rectifier/regulator dc connections and maybe the ammeter wires over, it's the same for Positive.
Colours for the wires are a matter of choice, as is fitting additional fuses and earths (can't have too many!) and also where to put any bullet connectors en route.
In the schematic, charging stuff is light blue, lighting pink and ignition yellow.
Basic ac wiring.pdf
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Re: How to fit electronic ignition

Postby clanger9 » Fri Feb 01, 2019 5:26 pm

Thanks Groily - that's pretty much exactly the same as my wiring.
Get rid of the complex alternator switching, use a solid-state rectifier/regulator and forget about the emergency circuit...
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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