Magneto: from manual to auto advance

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Re: Magneto: from manual to auto advance

Postby RayBeech » Fri Jul 01, 2016 9:02 am

This is the unit I built for my G9, admittedly it is not for everyone (or to everyons taste) I have access to Mill and Lathe also Alloy welding but it shows there are options.
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Re: Magneto: from manual to auto advance

Postby Reynard24 » Fri Jul 01, 2016 9:12 am

You could try contacting Martin Jay - the Distributor Doctor (01984 629540) he includes the 18D2 on the list of distributors he can refurbish and may be able to supply a reconditioned one.

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Re: Magneto: from manual to auto advance

Postby Groily » Fri Jul 01, 2016 8:50 pm

And reverting to the original point about the use of an ATD on a fixed timing magneto, spent a few happy hours chez moi talking to 'Nearly-mended Neil' from Kickstart Classics today, and he tells me that no fewer than three of his personal machines - twins - run with ATDs (built onto fibre gears). Confirmation that it has been done from One Who Knows.
I think they were a one-off small batch from a while back. Not the same as any other ATD gears in my box of bits, which cover Beesas Triumphs etc (apart from the sole modified AMC camshaft pinion I mentioned before).
I got the impression that drawings exist, and that just maybe they were, or still are, in the hands of the Club?

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Re: Magneto: from manual to auto advance

Postby RayBeech » Sat Jul 02, 2016 7:15 am

Not wishing to clog or sidetrack the thread, Bill, could I PM you about the body of what was on my G9 when I got it please?

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Re: Magneto: from manual to auto advance

Postby sunnybob » Sat Jul 02, 2016 10:17 am

I didn't know it is so difficoult to have ATD on a model 20 :shock: . I though it was something available at request at the time. So I will be very happy if there are any drawings about the ATD...
I live in Milano, Italy. Traffic is a nightmare and ATD will be very usefull in stop and go driving. Unfortunally I'm not a mechanic so I hope I could something I can fix on my bike.

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Re: Magneto: from manual to auto advance

Postby clive » Sat Jul 02, 2016 7:29 pm

Well I don't understand all the concerns about auto advance. On my G11CS with manual advance retard, I only retard it to kickstart it and once it is running I advance and then never touch it, town or on the open road. I know 650 and 500 twin owners who never touch the lever even to start.
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Re: Magneto: from manual to auto advance

Postby sunnybob » Mon Jul 04, 2016 1:49 pm

clive wrote:Well I don't understand all the concerns about auto advance. On my G11CS with manual advance retard, I only retard it to kickstart it and once it is running I advance and then never touch it, town or on the open road. I know 650 and 500 twin owners who never touch the lever even to start.


You are right, I do not use advance so much too. But I was wondering if a more precise use of the advance could partly prevent the black and sooty plugs....

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Re: Magneto: from manual to auto advance

Postby clive » Mon Jul 04, 2016 6:53 pm

Unlikely an auto advance retard would be more precise, it's only bob weights controlled by springs and tends to be open or closed. Black and sooty plugs are more likely due to on over rich mixture. I have an air filter fitted to my twin and have gone from 30 pilot jet to 25. Much improvement but still soots up if used in town.
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Re: Magneto: from manual to auto advance

Postby sunnybob » Fri Feb 09, 2018 10:25 am

Hi Folks,
I have found a 18d2 distributor with AMC gear to mount on my model 20 and I could try to go to auto advance, but how much power does an ignition coil absorb, please? Thank you.

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Re: Magneto: from manual to auto advance

Postby Groily » Fri Feb 09, 2018 1:37 pm

Not certain to the nth decimal point, but a 25W or so at a guess with a traditional points set-up, judging from ammeter movements - 2 Amps on a 12v system, 4A at 6v are roughly what I see. The points aren't closed all the time though, so the draw isn't constant. They're closed on a twin about half the time, bit more perhaps (not sure of the dwell on distributors). So average drain of not less than 2A on a twin on a 6v system?
Doesn't sound a whole lot - but at low speeds with lights on, could make a noticeable difference to things. Which I s'pose is why coil and battery was largely confined to alternator machines, a few exceptions excepted.

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