Ignition timing

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Mollbhan
Posts: 109
Joined: Sat Apr 06, 2019 11:52 pm
Location: Perthshire UK

Ignition timing

Post by Mollbhan »

Fitted a Thorspark unit to my 61 G12 some time back but was never sure if I got the timing right again. Ignition fully retarded the bike will start first kick without kicking back, tickover is slow with a very even beat. Still ticking over if the lever is set to full advance engine note becomes uneven but revs definitely increase. Performance on the road is good. Does this sound about right? I would definitely recommend the Thorspark to anyone who had a dodgy mag.
g5wqian
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Posts: 220
Joined: Wed Nov 18, 2015 7:43 am
Location: wiltshire
Location: near swindon wilts

Re: Ignition timing

Post by g5wqian »

that sounds about right .
my G11/MOD30 is much same .
my idle on full advance is jumpy but ok to leave it like that unless you want to retard it for any reason , of course the auto adv/retard ignitions give a better idle but if you dont have that you dont have it i guess !!
if you just run it at full advance on the road the only thing to listen for is when riding under load if you hear a pinking noise then back off the advance slightly until it stops doing this , i note that sometimes my bike runs fine with full advance and then sometimes it needs slightly less advance as it will pink on me , its most likely the petrol i have put in , i tend to use esso supreme but i notice it now says E5 on the pump when i go there so its got ethanol added plus it says 2 other additives as well , so perhaps its not quite as advanced as they say it is .

i may try the BP garage down the road next to see what thats like .

ian
cavalier90
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Posts: 4
Joined: Tue Jul 27, 2021 5:50 pm
Location: Devon UK

Re: Ignition timing

Post by cavalier90 »

I have fitted a Thorspark to my 42 G3L. It is not running yet so I checked the actual spark. Instead of a solid single spark, I get a crackle of sparks. Clearly this will completely confuse the timing. What is the spark at the plug like on your conversion? I sent a video to Sussex motorcycles and they said it looked fine. I can't believe that as it's the first time I've not had a single spark in many years of diy dabbling. Thanks.
Mollbhan
Posts: 109
Joined: Sat Apr 06, 2019 11:52 pm
Location: Perthshire UK

Re: Ignition timing

Post by Mollbhan »

I just get a single, substantial blue spark, if you get a series of sparks I wouldn't think it would upset the timing as long as the first spark comes at the correct time, the mixture will already be burning when the next sparks come.
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spookefoote1956
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Joined: Mon May 01, 2017 7:32 pm
Location: Wales Innit

Re: Ignition timing

Post by spookefoote1956 »

I use an Iridium plug with mine. They compliment each other well.
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