G15CS Carbs

Information relating to the Matchless G15 or AJS Model 33 750cc twin. This also includes the G15 Mk II and the G15/45
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Peter Morris
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Re: G15CS Carbs

Post by Peter Morris »

Hi,

Thanks for the help, I managed to take a look yesterday there was quite a lot of water in the distributor. Dried it out and now have a spark :D The knee hasn't recovered enough yet for me to be able to see if it starts/runs ok, but fingers crossed………

Not quite sure why it didn't break down on the way home from the Ardingly show (thats the only time the bike has got wet so far)… and started and run for 8 miles last Sunday before it decided something was wrong

Thanks again,
Peter
Groily
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Re: G15CS Carbs

Post by Groily »

Hope it's sorted now Peter.
However, I'm much interested in your experiences because I have recently been having similar 'issues' with my P11 (BB ignition and twin concentrics).
Starts well, usually; runs fine, sometimes; other times, it stops, as in cuts out stone dead - could be when cold, warm or hot, no rhyme or reason, it can happen in any throttle position, at any revs/load; sometimes restarts immediately without tickling or doing anything on the fuel side; other times, it won't; yet other times it starts but but then stops again, maybe after a few seconds, maybe after half a mile, maybe after a good while. On top of which, sometimes she misfires north of 4000 rpm, other times she doesn't. Maddening. No fuel blockages anywhere, nothing obviously wrong with any of the switch/coils/wiring, but here's a funny thing . . . quite often, if you switch the ign on and then off again (engine stopped I should add), there is a noise from I don't know where that is like the yowl of a cat in extreme pain, for a fraction of a second. What on earth is that? - could it be a noisy stream of sparks, or something?? Really weird, sounds a bit like the old noise for 'Miss' on Juke Box Jury back in the day, nearest I can describe for those old enough to remember (ie most of us).

Darned if I know, but summat is up with the thing and I'm not messing with it any more. Even if I got to the point where I thought I had fixed it, I still wouldn't be able confidently to say 'it's sorted', because it runs like a dream when it feels like it anyway.

So a mag is in process of going on (just need the correct sprocket for same, to replace the thing BB use with its roll pin and parallel shaft for the drive). The distributor housing and the twin 6v coils and the switch and wiring and all the solid state gubbins can go in the box that belongs to the bike for someone else to play with when I'm dead.

Then (of course), it'll be a fuel problem if/when things continue to play up and I'll have wasted my time! Oh well . . .
g80csp11
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Re: G15CS Carbs

Post by g80csp11 »

Bill (Groily) , I'd put money on the ignition switch being the problem , my P11 used to do the same , always start and then stop a mile , 5 , or 10miles later
new switch and all fixed
The BB system needs good volts
Groily
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Re: G15CS Carbs

Post by Groily »

I wouldn't disagree with any that at all Peter - it's just that it seems good whenever I play with it (as these things perversely do whenever you look at them)! I guess I could have just by-passed it or fitted something else for test purposes, but at the mo the thing is all a-dangle with bits of this and that hanging off, and I'll persevere with the mag option I think having got this far and ordered up a new sprocket.
While I'm on I'll be taking out the zener etc and fitting a decent modern rectifier/regulator. Then, I'll have my favourite option for 'reliable' (with all the original bits carefully saved) - magneto, alternator & good regulation. Less spaghetti too, and more room in the battery box for useful things like a few tools! The battery is a good 'un, no prob there with having enough volts to trigger things - been there and learnt that lesson with another BB-equipped bike I have. Thanks, Bill
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Peter Morris
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Re: G15CS Carbs

Post by Peter Morris »

Good luck with the mag Bill,

My bike has only covered 550 miles since a total rebuild but has run absolutely fine, even though the plugs soot up, apart from this episode....after the first time I took it out in the rain.

I will let you know what it is like as soon as my knee recovers enough to try and start it..........can't wait!!!

Peter
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Peter Morris
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Re: G15CS Carbs

Post by Peter Morris »

Knee recovered enough to give the bike a kick, it started FIRST KICK, and run perfectly fine......although I am not up to riding it just yet. So, back to the plugs sooting up problem!
Groily
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Re: G15CS Carbs

Post by Groily »

Glad to hear you're kneed up again Peter. Great news that your beast started so well too.
Equally good news here. A rebuilt manual mag on the P11, and first kick start last week when a correct new sprocket from Norvil turned up. She has started first or second kick every time since. Done about 500 miles in the week including one of our local rallies, and it is a bike transformed. I'm in love with it again. Runs far better and the alternator balances all loads (50W headlight) at under 1500 rpm. Capable of ticking over, retarded, at a barely credible 400 rpm on the tacho, sounding rather like a side valve single!
Now I can addresss some very fine outstanding carb tuning in the knowledge that the sparks department is good.
So there was something not right with the sexy BB system, but still no idea what. Bits are all safely in a box for the benefit of the next owner, who might just want his coils and switch sitting on their proper perches. Where that all sat there is now just an easily accessible engine STOP switch.
Only one drawback - and I expect anyone with a hybrid & magneto would say the same - is that access to the contact breaker end of the mag is a bit tight with the Matchless chaincase being 'higher' than the one on, say, a Dommie or an Atlas. And high pipes don't help one bit!
Cheers, Bill
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Peter Morris
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Re: G15CS Carbs

Post by Peter Morris »

Glad your bike is running well Bill, hope you enjoy it. I will have a bash at the carbs at the weekend to see if I can cure the plugs sooting up, will probably be on here again asking for help on Sunday evening. :)
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