G12 questions

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Istvan
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Posts: 6
Joined: Fri Nov 01, 2019 7:05 pm
Location: HUNGARY

G12 questions

Post by Istvan »

Hallo ,

Thank you for joining in the club ! I'm still nem here .
I have a G12 , 1959 . I would have more questions about that . I would to know where the paper seal that is between the crankcase halves ( 015034 ) should be installed ? I don't see a place in the crankcase where this should be inserted . I didn't find such a seal in the engine during disassembly . Can someone tell me how thick this papier is ? I would make it myself .
My other question is : does the crankshaft needs the bearing in which the basket is made of bronze ? Or does it fit which steel basket ?
I apologise for the poor spelling . My english is pretty weak .
Thanks in advance for the answers !

Best regards :
István
cbranni
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Joined: Sat Oct 09, 2010 9:17 pm
Location: ABERTAWE UK

Re: G12 questions

Post by cbranni »

Hi Istvan, welcome to the club, ...........udvozlet!

There should be a paper gasket and the thickness is .25mm, I would use the bearings with steel basket others may not agree.

Colin

Nothing at all wrong with your English my friend, better than my Hungarian
only dead fish go with the flow
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dave16mct
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Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: G12 questions

Post by dave16mct »

The paper gasket goes at the front of the crankcase where the oil filter gallery is. It will leak oil if you leave it out. Some members have machined a groove for an 'O' ring which works very well.
Dave.
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1608
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Joined: Mon Oct 05, 2009 1:00 am
Location: ESSEX UK

Re: G12 questions

Post by 1608 »

I think Istvan is asking where the thin circular gasket goes, its not obvious as there is no recess. The gasket is fitted between the crankcase
halves to seal the oil filter tunnel.

Beat me to it Dave.
Istvan
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Posts: 6
Joined: Fri Nov 01, 2019 7:05 pm
Location: HUNGARY

Re: G12 questions

Post by Istvan »

Thank you very much for the quick answer !
I'm trying to take a photo of my engine block and upload it here because I don't see anywhere where that seal should be .

Best regards :
István
cbranni
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Joined: Sat Oct 09, 2010 9:17 pm
Location: ABERTAWE UK

Re: G12 questions

Post by cbranni »

I read that all wrong, I read the post for chaincase to crankcase gasket then read this one and got it all wrong .............ignore me, I'll get my coat.

Blame the lockdown. all I can add is the paper gasket is about .1mm thick, very thin paper
only dead fish go with the flow
JEAN-NOEL
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Joined: Wed Oct 12, 2005 10:45 pm
Location: FRANCE

Re: G12 questions

Post by JEAN-NOEL »

Hello Istvan,
I agree with Dave. If you have access to a workshop facilities it is better to mill a groove in one crankcase half to fit an "o" ring 28 x 1.5 mm. You can search topics regarding this question on the forum. To have an oil-tight engine it is essential to check the flatness of the two half crankcases on a thick glass, and to rub them with grinding paste until they have a very uniform color. If the gudjon holes are "raised", you may slightly countersunk them with a larger drill bit. The most critical points are : the filter tunnel, the oil gallery at the top of the casings, and the oil channels to the rocker arms.
Cheers.
Istvan
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Posts: 6
Joined: Fri Nov 01, 2019 7:05 pm
Location: HUNGARY

Re: G12 questions

Post by Istvan »

Hallo !

Thank you for your answers ! The machining of the o-ring has been solved . Just uploading the image isn't going yet .

Best regards :
István
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