Starting problems when warm

Information relating to the Matchless G11 or AJS Model 30 600cc twin
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lasse
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Joined: Wed Oct 12, 2005 10:45 pm
Location: SWEDEN

Starting problems when warm

Post by lasse »

Hi all.I am new on this forum.I have a AJS 30 CS from -58.He start quite easy when cold,but I kick my knee out of funktion when he is hot or warm.I have tested the magneto in my own test,it gives sparks 6 mm long when cold.I have seen somewhere.that it is more difficult to get a spark under compression.What is the problem?
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dave16mct
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Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: Starting problems when warm

Post by dave16mct »

The most likely cause is the condensor in the magneto has broken down. You can fit a Brightspark 'Easycap' condensor on the points plate but the old one needs to be disconnected and its buried in the end of the armature. Google Brightspark Magnetos to see the details.
Dave.
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Ralph
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Joined: Tue Jan 07, 2020 7:00 pm
Location: UK

Re: Starting problems when warm

Post by Ralph »

Have you tried the spark when it's hot?
when electrics start to fail they very often
fail when hot but will work once cooled
down, I would suspect the condenser.
Ralph

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bitza
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Posts: 452
Joined: Tue May 27, 2003 1:00 am
Location: SHROPSHIRE UK

Re: Starting problems when warm

Post by bitza »

Magneto first to check, quite common fault with age.
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Duncan
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Joined: Thu Jul 10, 2003 1:00 am
Location: HAMPSHIRE UK

Re: Starting problems when warm

Post by Duncan »

Sounds like a magneto/condenser issue but check some other simple things first like:
Do you have an insulating spacer between the carburettor and inlet manifold?
Is the engine running lean/is there an air leak on the manifold?
Are you valves/tappets correctly adjusted?
Are the HT leads in good condition and the spark plugs and plug cap?
Have you owned the bike for long, has it always been like this?
MalcW
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Joined: Tue Oct 24, 2017 12:05 pm
Location: DEVON UK

Re: Starting problems when warm

Post by MalcW »

My G12 has had a full magneto rebuild but is still harder to start when hot. But genuine Champion spark plugs, and giving it a swift kick withOUT retarding the ignition have helped a lot.

Malc
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clive
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Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: Starting problems when warm

Post by clive »

dave16mct wrote:The most likely cause is the condensor in the magneto has broken down. You can fit a Brightspark 'Easycap' condensor on the points plate but the old one needs to be disconnected and its buried in the end of the armature. Google Brightspark Magnetos to see the details.
Dave.
I agree with this, had to do it on a rebuilt mag after about 6 months of use which came with my 1958 G11CS. I was lucky and the "condensectomy" as described on the website was easy to do. I bought two Bright Spark units keeping one as a spare taped in the headlight in case the first gave up the ghost. Never got it out in the last 5 years except to show people what the Bright spark unit was like!
clive
if it ain't broke don't fix
lasse
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Posts: 7
Joined: Wed Oct 12, 2005 10:45 pm
Location: SWEDEN

Re: Starting problems when warm

Post by lasse »

Thankyou for all advise.I have now put in the Spark Bright things and now it will start even warm.
G15 Roy
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Location: ESSEX UK

Re: Starting problems when warm

Post by G15 Roy »

clive wrote:
dave16mct wrote:The most likely cause is the condensor in the magneto has broken down. You can fit a Brightspark 'Easycap' condensor on the points plate but the old one needs to be disconnected and its buried in the end of the armature. Google Brightspark Magnetos to see the details.
Dave.
I agree with this, had to do it on a rebuilt mag after about 6 months of use which came with my 1958 G11CS. I was lucky and the "condensectomy" as described on the website was easy to do. I bought two Bright Spark units keeping one as a spare taped in the headlight in case the first gave up the ghost. Never got it out in the last 5 years except to show people what the Bright spark unit was like!
Now where did I put it. :lol:
Roy
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clive
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Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: Starting problems when warm

Post by clive »

lasse wrote:Thankyou for all advise.I have now put in the Spark Bright things and now it will start even warm.
Thats good news Lars. How about a photo?
clive
if it ain't broke don't fix
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