G9 (57) Intermittent ignition problems

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Colin Kent.
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Joined: Wed Oct 12, 2005 10:45 pm
Location: AUSTRALIA

G9 (57) Intermittent ignition problems

Post by Colin Kent. »

After a full magneto overhaul / recondition only 350 miles ago, the ignition has failed twice on the road, after runs of 10/15 miles. After the previous failure, the magneto was removed and checked and pronounced OK, and the engine restarted and ran without problems. This time, breaker gap OK, HT continuity OK, engine started once with plug gaps reset to 0.012 in, but would not continue to run, or restart.
Any tips for futher checks before magneto removal ?
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silverarrow
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G9 (57) Intermittent ignition problems

Post by silverarrow »

Colin,

I had a plug give me these very symptoms, albeit on a single, but perhaps worth illiminating. A faulty condensor might also give you the symptoms you describe.

Hav a spare plug with you so that next time you get a failure you can quickly attach to the plug lead and prove what sort of failure you have as it could also be something as simple as the fuel tank not being vented. This happened to my Silver Arrow at this years Jampot Rally.

Good luck.

Les Smith
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Colin Kent.
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G9 (57) Intermittent ignition problems

Post by Colin Kent. »

Greetings Les,
Thanks for that, but new plugs already tried with no result. Can you perhaps point me to any Jampot "Technical Topics" articles on in situ magneto testing to save the long manual slog through all my back copies, before I remove the magneto (again).

Regards, Colin Kent
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TommoT
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G9 (57) Intermittent ignition problems

Post by TommoT »

Colin try this website:

http://members.aol.com/Pinman1/magnetos.htm

All possible faults and testing methods described here! Your fault could still be the magneto; age-related secondary armature winding break-down, allowing the mag to function when cold, but failing when warmed up!

Good luck
Tom M. (TM)
TommoT

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Ian Stack.
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Location: Victoria AUSTRALIA

G9 (57) Intermittent ignition problems

Post by Ian Stack. »

Hi, I tend to agree with Les,as I think his main point with having a spare plug handy is so when the problem occurs again,a quick spark condition test can be carried out on the side of the road.A little tip is to braze an alligator clip to two sparkplugs as a testing tool which can be attached to the barrel or casing & will determine how good a spark is under the running conditions remembering it will be under more stress when in the combustion chamber.If the spark is a nice blue crack,obviously start looking at the fuel system.I hope this may help to pinpoint your problem.My general conclusion in MOST cases is to keep things simple.Good luck.
Adrian Pancaldi
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G9 (57) Intermittent ignition problems

Post by Adrian Pancaldi »

I think Les was right on the money with suggesting the condenser.One of my mates had the K2f on his Norton twin reconditioned ,and the same thing happened. It was removed, bench tested and pronounced O.K.The machine let him down again.The test found it to be good again,but the condenser was changed as a precaution,and the
problem hasn't re-occured in 35,000 miles.
Regards
Adrian Pancaldi
JEAN-NOEL
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G9 (57) Intermittent ignition problems

Post by JEAN-NOEL »

Yes, this problem is generally caused by the condenser : good when it is cold, bad when it is warm.
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