G9 Cylinder Boring

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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garycolwill
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Joined: Sun Mar 21, 2021 6:58 pm
Location: California

G9 Cylinder Boring

Post by garycolwill »

Reading through the spares list, for my '51 G9 engine there is a section called "RE-BORING" that says the cylinders can be bored .020 or .040 inches oversize and pistons/rings acquired that fit (#018025). Are these pistons and rings still available, and has anyone here had experince with this? If so, was it worth doing? Any probs?
Last edited by garycolwill on Sat May 08, 2021 9:16 pm, edited 2 times in total.
garycolwill
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Re: G9

Post by garycolwill »

Sorry - meant to thread title to be "G9 Cylinder Boring"
Mick D
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Re: G9

Post by Mick D »

garycolwill wrote: Fri May 07, 2021 8:36 pm Sorry - meant to thread title to be "G9 Cylinder Boring"
Hi

If you click on the edit button, (the pencil top right), you can amend the title - but then, a computer savvy American would work that out wouldn't they ;) ;) :rofl: :rofl: (My humour)

Regards and welcome to the Club Mick
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clive
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Re: G9

Post by clive »

You would be very lucky to find original piston and rings but aftermarket ones are about probably up to 60 thou oversize. As to whether it is worth doing, that depends if the current bore is worn out or damaged. If not you are just pouring money away....save it and join the club. :rofl:
clive
if it ain't broke don't fix
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Duncan
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Re: G9

Post by Duncan »

Hi Gary

If the bores and pistons are good it is possible to just fit replacement rings (modern replacement pistons have different ring thickness so you need some for your specific piston), there are UK companies that supply them but I would imagine you could find some nearer to home, if removing the pistons get new circlips for refitting.
garycolwill
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Re: G9 Cylinder Boring

Post by garycolwill »

In terms of performance, would this increase capacity enough to make a difference? I haven't had the chance to take the top of and have a look at the cylinders, but if they're ok, I will probably just leave them as is. Just curious about performance is all.

I did join, btw. I guess I need to log off and use the new user name (garycolwill2) for that to show.
SPRIDDLER
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Re: G9 Cylinder Boring

Post by SPRIDDLER »

No, you won't notice any performance increase from the small capacity change.
It might run better (and burn less oil if it's smoky now) from having new rings.

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garycolwill
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Location: California

Re: G9 Cylinder Boring

Post by garycolwill »

Will do - thanks.
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