Odd problem with ignition

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Expat
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Location: Tennessee, USA

Re: Odd problem with ignition

Post by Expat »

I was alluding to your signature "I poke badgers with spoons" where did you find that?
That comes from an Eddy Izzard routine. He's seeking forgiveness of that sin in the Confessional box at church. It appeals my ridiculously childish sense of humour.
It's the sort of pastime I might find fulfilling when too old to ride any more.[/quote]

SPRIDDLER.....Eddie Izard......a comic genius. Me and my wife think he is hilarious, we refer to the numerous gecko lizards out here as Eddie's.

:lol: :lol: :lol: :rofl: :rofl: :rofl:

I'm grinning just thinking about it now. :beer:
Keep shiny side up.

These are my principles, if you don’t like them, I have others. (Groucho Marx)
rajeshnair
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Joined: Thu Dec 10, 2015 10:34 am
Location: KARNATAKA INDIA

Re: Odd problem with ignition

Post by rajeshnair »

Magneto is recently serviced,same problem when I switched to different magneto( I have a few Mags in good working order).When I pulled out the magneto and ran it on the bench it fires on both plugs.On the bike only one cylinder fires,and when I remove the firing cylinders plug cap the other cylinder begins to fireplug leads are copper and cap has no resistor.Cheers
JimFitz
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Location: Kent, England

Re: Odd problem with ignition

Post by JimFitz »

I would agree with Albert and Groily on this one. Soft brushes causing a layer of carbon over the slipring and the spark taking the path of least resistance.
On my Super Rocket I have just finished cleaning the slipring as best I can and I have a new pair of pickups, acorns and brushes on order from Brightspark. My old brushes were like an HB pencil when I tried drawing with them on paper. I did not trust the pickups either. All made in China probably.

Jim
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.
aobp11
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Re: Odd problem with ignition

Post by aobp11 »

Rajesh,you say the mag fires both plugs when tested on the bench (and both plugs connected at the same time I suppose). Do you use plugs or spark gaps for this of sufficient gap width? Say 5 mm? What happens when you use one gap of about 5 mm and at the other side a normal plug (less than 1 mm gap)? Does the 5 mm gap still fire then?

Albert
g80csp11
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Re: Odd problem with ignition

Post by g80csp11 »

Had a similar issue on my G15 recently , one cylinder just would not run correctly , you could feel the difference in the exhaust , and misfiring spitting back through the inlet
eventually after 2 weeks checking ignition , carburettors , valve timing etc. it turned out to be the new exhaust system fitted during the rebuild
down pipe , was so close to the internal silencer baffle that it produced excessive back pressure
mismatch of exhaust and downpipe . all sorted now

Is this a new problem , or have you changed several parts at the same time
rajeshnair
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Joined: Thu Dec 10, 2015 10:34 am
Location: KARNATAKA INDIA

Re: Odd problem with ignition

Post by rajeshnair »

IIRC this could be caused by a dirty slipring. The "spark current" prefers to flash over the slip ring surface to the opposite cable brush since the non-active cylinder has low compression at that moment.

Turns out that this was exactly the problem,my brand new pickup brushes were soft and was leaving a coating of carbon on the slip ring.I cleaned out the slipring and the bike fired first kick and idles like music.Thank you gentlemen for your quick response,ive been restoring bikes for the last 25 years and this is the first time ive faced this problem.I guess one never stops learning.the new brushes I bought were made in india,probably off a HB pencil! :lol: :beer:
R_Nairtvm
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Joined: Thu Jan 25, 2018 3:42 am
Location: India

Re: Odd problem with ignition

Post by R_Nairtvm »

rajeshnair wrote: Turns out that this was exactly the problem,my brand new pickup brushes were soft and was leaving a coating of carbon on the slip ring.I cleaned out the slipring and the bike fired first kick and idles like music.Thank you gentlemen for your quick response,ive been restoring bikes for the last 25 years and this is the first time ive faced this problem.I guess one never stops learning.the new brushes I bought were made in india,probably off a HB pencil! :lol: :beer:
Good to hear you've sorted the issue.

Aren't the good'ol TVS Brushes still available in the market? Suppose you could reverse engineer one for the Twin from original TVS ones ?

Best Regards & Ride Safe

Ram
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