G 12 CSR Pistons help..please

Information relating to the Matchless G12 or AJS Model 31 650cc twin
maurizio66
Posts: 20
Joined: Sat Mar 26, 2016 7:34 pm
Location: italy

Re: G 12 CSR Pistons help..please

Post by maurizio66 »

I weighed my JP +20 and like Groily I found +/- 466g, could be nice to know the same GPM weight. Do you know the recommended clearance in the box from JP +20 as I would like to compare with my actual bore and check if it's right or too tight,

ciao Maurizio
JEAN-NOEL
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Joined: Wed Oct 12, 2005 10:45 pm
Location: FRANCE

Re: G 12 CSR Pistons help..please

Post by JEAN-NOEL »

Hi Maurizio,
about the wheight of a +0.20 piston GPM 8.5 CR you can ask : spares@jampot.com
This item is on their shelves !
J.N.
maurizio66
Posts: 20
Joined: Sat Mar 26, 2016 7:34 pm
Location: italy

Re: G 12 CSR Pistons help..please

Post by maurizio66 »

I have tried to find GPM pistons in Italy but +20 are out of stock and Gandini don't know if they will repeat,
So I have ordered at Amoc trough the site and i have received JP pistons, probably even Amoc are out of stock with GPM. I have a question as on the compression rings that i have received with JP I can't see any chamfer, dot or TOP even with a magnifier, how is the right way for fitting the rings? Meabe every side are correct?

Thank you for your help, Maurizio
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ajscomboman
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Location: HAMPSHIRE UK

Re: G 12 CSR Pistons help..please

Post by ajscomboman »

You wouldn't have got JP pistons through the club as we only stock GPM.
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Stuoyb
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Location: BEDFORDSHIRE UK

Re: G 12 CSR Pistons help..please

Post by Stuoyb »

The only source of the high compression used to be JP, it is possible that there is some residual stock on some sizes.

If there are no markings on the rings then there is no restriction on which way up they can be fitted.
maurizio66
Posts: 20
Joined: Sat Mar 26, 2016 7:34 pm
Location: italy

Re: G 12 CSR Pistons help..please

Post by maurizio66 »

ajscomboman wrote:You wouldn't have got JP pistons through the club as we only stock GPM.
Of course i have bought pistons and others parts trough the club at Amoc, I have also received an e mail from Stuart that invite me to order the day after as the price of the piston will be lowered due to a new stock, that was very kind from him, in fact the price was cheeper. I don't know between JP and GPM which one is better, I only know that GPM fit good compression rings. If possible I will try to lighten theese heavy pistons when I will send to the machine man.
Any suggestions is appreciated,
Thank you, Maurizio
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