Replacement Piston Rings

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Martin.S
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Replacement Piston Rings

Post by Martin.S »

When piston rings aren't available how do you determine the dimensions required when you only have a bare piston.
I have a bare G12 piston but no rings, the outer diameter is obvious but the thickness and inner diameter not so - what sort of clearances are required?
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cbranni
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Re: Replacement Piston Rings

Post by cbranni »

I would speak to Ian at Cox and Turner

https://www.coxandturner.co.uk/piston-rings

Colin
only dead fish go with the flow
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Rob Harknett
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Re: Replacement Piston Rings

Post by Rob Harknett »

when you say about outer dia obvious, does that mean you see on the piston crown, STD, or oversize .020" etc.
http://archives.jampot.dk/technical/Pis ... models.pdf
http://archives.jampot.dk/technical/Pis ... x-1962.pdf.
Check your bikes parts list and workshop manual for your answers to, clearance etc..
It has been said new repro pistons will need new repro rings to suit them. Not NOS unless your pistons are of the old type manufacturer,
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cfaber
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Re: Replacement Piston Rings

Post by cfaber »

cbranni wrote:I would speak to Ian at Cox and Turner

https://www.coxandturner.co.uk/piston-rings

Colin
This. They have loads of new old stock and can build what you need based on model and piston type
Fix it until it's broken!

Otherwise how will
anything get done?
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Martin.S
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Re: Replacement Piston Rings

Post by Martin.S »

"Check your bikes parts list and workshop manual for your answers to, clearance etc.. " - Mmmm - cant find any reference other than ring gap."
What I did find is this from Rick Edwards - Post 1960 rings for Original and Hepolite are radially thicker than pre 60. ie 56-59 600cc and 650cc pistons are 0.109" post 60 rings are 0.116". You can put 109's in later pistons , but not the other way round for obvious reasons.
That sorts out the radial clearance - I've now bought the 0.109" rings for my post 1960 piston.
What I don't have now is the side clearance.
39speedtwin
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Re: Replacement Piston Rings

Post by 39speedtwin »

I bought for my 1937 G8 Clubman from C&T last week, quoted the piston number and size, arrived next day. Good service.
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Martin.S
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Re: Replacement Piston Rings

Post by Martin.S »

Just received my Wellworthy "Mile Master" piston rings and on their packets it states - Minimum vertical clearance 0.0025".
Cheers
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