G12 CSR engine noises

Information relating to the Matchless G12 or AJS Model 31 650cc twin
poptsova
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Location: hampshire

Re: G12 CSR engine noises

Post by poptsova »

hello mark dont give up if you like i will come and look also and if you would like me to help i will strip the engine if we cannot locate the problem i have been working on these engines for many years now. and now i am building another engine for another member . i live in hampshire but the other end but dont mind helping dave
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clive
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Re: G12 CSR engine noises

Post by clive »

I agree with Rob Currie that it could be a worn slide in the carb. This can cause a rattle at lower revs and it could also be responsible for poor tickover. Easy to check, ride along at the speed you hear the rattle and stick one finger in the carb bellmouth and if the rattle stops you have found the problem. If it doesn't you have eradicated one possible problem and have not even got the tools out!
clive
if it ain't broke don't fix
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1608
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Re: G12 CSR engine noises

Post by 1608 »

I think its a bit more than just a rattly carb slide. If thats all it is then its been a big fuss over nout. I recall earlier in the post that even kicking the thing over assaulted the ears. Interested to know what it turns out to be after all this. Let us know please Mark.
ajsm18
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Re: G12 CSR engine noises

Post by ajsm18 »

bestaeva wrote:hello mark dont give up if you like i will come and look also and if you would like me to help i will strip the engine if we cannot locate the problem i have been working on these engines for many years now. and now i am building another engine for another member . i live in hampshire but the other end but dont mind helping dave
Hello Dave,
Thank you for the offer of help, you may well live to regret it! I'm concentrating on the 'new' lightweight I bought last month at the moment and have the electrics dismantled on the twin but, when I get started again, I may well be in touch for some help.
Thanks again
Mark
ajsm18
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Re: G12 CSR engine noises

Post by ajsm18 »

Thanks, everyone, for all the help. I've been chatting to various club members at autojumbles recently and, as well as all of the suggestions and advice I've had for everyone here, I will start stripping the top end down, when I get the chance.

I don't think it is a loose throttle slide but will definitely check that first. I know the taking apart will be easy, it's the putting back together again that I will struggle with!

All the best

Mark
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clive
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Re: G12 CSR engine noises

Post by clive »

Use lots of pots to separate parts and make sure they go back on the correct side as there will be wear, make a note of order parts go back as you disassemble them, but don't count on previous owner having assembled them correctly in view of noises. Look out for any witness marks showing that something is touching which shouldn't. I completely stripped down my G11CS last winter, first time I had worked on a twin. Most of it was fairly straightforward (after a bit of research on the bits I had failed to note order!), your problem is likely to be working out what is acceptable wear and what is knackered. You will get support from the website but if there is someone locally with experience all the better. Good luck.
clive
if it ain't broke don't fix
ajsm18
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Re: G12 CSR engine noises

Post by ajsm18 »

Hi Clive,
Thanks for the advice. As a teenager, I stripped down then engine in my Triton and both of the BSA A65s that I had but, somehow, as a grown-up, it all seems more complicated now! i suppose it is largely because I didn't care much (or didn't know any better) if the oil stayed inside or on the outside!
Mark
JohnHewes
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Location: NORTHANTS UK

Re: G12 CSR engine noises

Post by JohnHewes »

I quite agree Mark, I am also much more circumspect these days, I remember stripping the G9 crankcases to try to stop an oil leak from between the cases near the oil filter chamber in the back garden of a house where I was in digs in 1967.
I had seen a tip in Motorcycle Mechanics to wrap a few rings of cotton thread around the crankcase faces at this point so I wanted to try it.
No help from a forum in those days!
Now I think I must have been mad. I had nowhere to work except the back step!
It didn't make much difference, but as you say that didn't seem to matter so much then, all the bikes leaked, some more than others. Now we want them perfect but they never were.

John
ajsm18
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Re: G12 CSR engine noises

Post by ajsm18 »

Hi John,

I'm too embarrassed to tell you about using a hammer to fit the barrel on the 500 AJS I had as a kid in the 70s! Ooops, I've told you. It was a field bike with a 1948 Model 18 engine in a later Jampot frame and I was 14/15 when I found it in a neighbour's garden. Having persuaded the owner to let us have it, a couple of mates and I had great fun learning about old bikes and, only occasionally, riding it.

I'd bought some new rings and struggled to refit the barrel so resorted to a hammer. My "kind" mate even mentioned the event in his best man's speech at my wedding!

I'm not sure that my abilities have improved all that much since then :D

Regards

Mark
ajsm18
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Re: G12 CSR engine noises

Post by ajsm18 »

Good morning all,

After raising the issue of my noisy G12 some years ago (!) I have finally decided I need to take a look inside and so have started taking the engine to bits. On draining the oil, the magnet in the sump plug was covered with iron filings so I guess that may indicate that the cam followers are worn as I couldn't think what else would have worn so much that was made of steel.

Before I lift the cylinder heads, I wondered if it would be possible to measure valve lift at the valve or pushrod end and whether this would indicate that one or more of the cam followers had worn away? Are these measurements published anywhere? I can't find any reference to amount of valve lift in any of the reference material I have but I may not have looked hard enough yet!

I thought followers were rare so wondered about getting them rebuilt and stellited (?) but see that the club spares scheme lists them so I guess I could just replace them. I'm not looking forward to stripping the engine that far, though :(

Any thoughts or advice is very gratefully received.

Thanks

Mark
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