Carb question.

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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clive
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Location: LONDON UK

Re: Carb question.

Post by clive »

ColourNcoat wrote:....... It does stick in my gut that I have to spend yet more money on this little treasure to finally get it done.
I know you can't put a price on everything but in this case I have to draw a line somewhere, yet I have to get it finished.
How many people have spent more than something is worth without having sentimental attachments?
Regards
I would say most people who do up an old bike end up spending more on it than it is worth unless they do all the paintwork and mechanical work themselves and had purchased it at a good price. If they keep it some years and see the value rise they may cover the expenditure but If you do keep it and use it in the interim you will probably spend more time and money on keeping it running. Try owning 6 bikes! :beer:
clive
if it ain't broke don't fix
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Duncan
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Re: Carb question.

Post by Duncan »

A concentric may be a cheaper option or even a wassell AMAL copy if originality is not a major concern and a budget has to be worked to, perhaps any one who has made this modification on a G2/14 could confirm their settings for you?
Mick D
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Location: Aberdeenshire

Re: Carb question.

Post by Mick D »

Hi

You probably don't 'need' a new carb if you are prepared to accept slightly less than optimal tick-over. This carb, from one of my recent restorations is an original from 1958 and is now back in use:
Crud.png
Crud II.png
Crud III.png
A new carb will have no wear between the slide and bore so will improve slow running, it will also have clean galleries and new jets etc. so that's your best chance of making a serious step forward.

If you budget is tight and you can live with a slightly erratic tick over, (I do and I'm sure I'm not alone), I would thoroughly clean the carb, (which you say you have already done), and replace the pilot jet, (£6), then set the slow running as per one of the documents previously linked. If it turns out not to be the pilot jet it's cost you £6 and you now have a spare :)

Just a thought - how are you installing the pilot jet? it should be fully screwed into the carb body and then the cap fitted, (not screwed into the cap and then installed into the body).

Regards Mick
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ColourNcoat
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Location: Monmouthshire UK

Re: Carb question.

Post by ColourNcoat »

Duncan wrote:A concentric may be a cheaper option or even a wassell AMAL copy if originality is not a major concern and a budget has to be worked to, perhaps any one who has made this modification on a G2/14 could confirm their settings for you?
Hi Duncan,

Its not so much of a cheaper option, its more to do with a resolve for the outlay. ;)
If its a fifty pound outlay or a two hundred pound outlay and its still not fixed :roll:
Thanks for the options :beer:
Regards
Roger
ColourNcoat
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Location: Monmouthshire UK

Re: Carb question.

Post by ColourNcoat »

Mick D wrote:Hi

You probably don't 'need' a new carb if you are prepared to accept slightly less than optimal tick-over. This carb, from one of my recent restorations is an original from 1958 and is now back in use:
Crud.png
Crud II.png
Crud III.png
A new carb will have no wear between the slide and bore so will improve slow running, it will also have clean galleries and new jets etc. so that's your best chance of making a serious step forward.

If you budget is tight and you can live with a slightly erratic tick over, (I do and I'm sure I'm not alone), I would thoroughly clean the carb, (which you say you have already done), and replace the pilot jet, (£6), then set the slow running as per one of the documents previously linked. If it turns out not to be the pilot jet it's cost you £6 and you now have a spare :)

Just a thought - how are you installing the pilot jet? it should be fully screwed into the carb body and then the cap fitted, (not screwed into the cap and then installed into the body).

Regards Mick
Hi Mick,

My carb wasn't that bad :rofl:
I see exactly what you are saying and if that can be brought back to life, there is still hope :D
The port on my bike is 1 1/8 and the 376 is 1 1/16 so would this make a big difference?

Sorry to all for going back and forth :oops:
Regards
Roger
Mick D
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Re: Carb question.

Post by Mick D »

Sorry - forgot about the throat mismatch.

There will be a pressure drop as the air fuel mixture transits over the step, this can cause the fuel vapour to partially condense and may result in poor running. You could blend the different diameters together over the length of the insulator which would minimise the effect but ideally the carb needs to be matched to the head.

Give blending a try if your insulator will allow it, it's free, and replace the pilot jet.

Regards Mick
ColourNcoat
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Location: Monmouthshire UK

Re: Carb question.

Post by ColourNcoat »

Mick D wrote:Sorry - forgot about the throat mismatch.

There will be a pressure drop as the air fuel mixture transits over the step, this can cause the fuel vapour to partially condense and may result in poor running. You could blend the different diameters together over the length of the insulator which would minimise the effect but ideally the carb needs to be matched to the head.

Give blending a try if your insulator will allow it, it's free, and replace the pilot jet.

Regards Mick
This was previously mentioned by Clanger who kindly put up a link on the subject. I did do a port match and made brass bushes to stop gasket/insulator misalignment. Unfortunately this didn't make any difference or improvements. :cry:
Just when I think there could be a possibility of a fix its a case of biting the bullet and get a new 389/82. :beer:
Regards
Roger
ColourNcoat
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Re: Carb question.

Post by ColourNcoat »

Big thank you to everyone for the advice given and have just ordered a new 389/82 from club spares so thanks and fingers crossed :beer:
Regards
Roger
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Samuel
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Location: Somerset UK

Re: Carb question.

Post by Samuel »

ColourNcoat wrote:Big thank you to everyone for the advice given and have just ordered a new 389/82 from club spares so thanks and fingers crossed :beer:
Regards
As I suggested on 11th February. Pleased you arrived at that conclusion. :-)
Sam
ColourNcoat
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Location: Monmouthshire UK

Re: Carb question.

Post by ColourNcoat »

Samuel wrote:
ColourNcoat wrote:Big thank you to everyone for the advice given and have just ordered a new 389/82 from club spares so thanks and fingers crossed :beer:
Regards
As I suggested on 11th February. Pleased you arrived at that conclusion. :-)
And thank you for that Sam :beer:
It's because it still wouldn't have been right because the carb was a mismatch for my cylinder head. Besides I was probably getting on everyone's nerves :D :oops:
Time will tell :beer:
Roger
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