G12 rear shocks

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Nostromo
Posts: 44
Joined: Sat Jun 23, 2012 5:40 pm

G12 rear shocks

Unread post by Nostromo » Fri Jul 20, 2012 1:25 pm

Hi again - The Matchless G12 rear shocks I have (possibly aftermarket) are the ones that can be dissassembled unlike the originals that are crimp sealed (or so I'm told). As they are indeed currently in bits - does anyone know a) what type of oil I should use to refill them (I'm thinking ATF maybe) and b) what quantity?

Thanks

Ian

The Mighty Gusset

Re: G12 rear shocks

Unread post by The Mighty Gusset » Fri Jul 20, 2012 2:17 pm

Certainly it's ATF for front forks, I can't say I've ever tried rebuilding a set of rear shocks before.

DAVE M2
Posts: 539
Joined: Wed Sep 23, 2009 11:52 am

Re: G12 rear shocks

Unread post by DAVE M2 » Fri Jul 20, 2012 4:06 pm

http://archives.jampot.dk/Book/Workshop ... 7-1966.pdf" onclick="window.open(this.href);return false;

any good?

doesn't imply that you can refill them.

If you use the book, they ask for donations to the site

cheers

Nostromo
Posts: 44
Joined: Sat Jun 23, 2012 5:40 pm

Re: G12 rear shocks

Unread post by Nostromo » Fri Jul 20, 2012 7:16 pm

Thanks for your replies. Yep - this seems to be a bit of a weird one. Everyone I talk to swears there are are no such things as "dismantleable" "refillable" rear shocks for a Matchless G12 yet that's what I have. To prove it here's a pic.
rearshock.jpg
No one seems to know anything about these!!! - I talked to a guy from Hagon who'd never heard of them and also a guy who does replica girling and he'd never heard of them either.... I guess I'll just have to stick "some" amount of ATF in them and see what happens....

Ian

The Mighty Gusset

Re: G12 rear shocks

Unread post by The Mighty Gusset » Fri Jul 20, 2012 9:11 pm

I think I've got an article on rebuilding shocks, and experiments with oil somewhere lying around, possibly in a recent issue of Classic Mechanics, I'll see if I can find it, and see if it says anything useful.

The Mighty Gusset

Re: G12 rear shocks

Unread post by The Mighty Gusset » Fri Jul 20, 2012 9:28 pm

Found it !
Or part of it at least !
The May 2012 issue of Classic Motorcycle Mechanics sees part 2 of a Mark Haycock article on rebuilding a pair of Marzocchi shocks and deals with refilling with oil.
I think part 1 might have dealt with stripping down and acquiring a spares kit, but I've not found that issue yet.
I'm thinking that perhaps, because your shocks are :
a) Red
b) Rebuildable
That they might possibly be Marzocchi's ?
Anyway, I digress, back to the article :
In short, he measured down from the top of the shock body, with the internals removed, and came up with an oil level of 70mm from the top of the damper body down to the surface of the oil.
For oil viscosity he experimented with dropping things into different oils and decided that SAE 2.5 was probably ideal, but as he didn't have any, decided to settle on some SAE 5 synthetic fork oil that he'd scored cheaply off Fleabay.
If you want to read both articles in full then I suggest you contact M*rton's Media (aka The Evil Empire) and purchase a couple of back issues, otherwise I hope my edited highlights will be of some help to you.
Good Luck !

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Hooli
Posts: 10185
Joined: Thu Feb 19, 2009 11:52 pm
Location: Doncaster

Re: G12 rear shocks

Unread post by Hooli » Fri Jul 20, 2012 11:37 pm

I was about to say fork oil of some type, but Gus beat me too it.

It's not classics but the rear shocks on GSX14s tend to burst & people found that they could be refilled with 10w fork oil quite well. I'd assume a lighter bike probably needs lighter oil, but if you don't like the ride it won't be that difficult to change the viscosity will it?
Classics ain't built in Metric

livinginthepast
Posts: 12
Joined: Mon Oct 26, 2009 1:36 pm

Re: G12 rear shocks

Unread post by livinginthepast » Sat Jul 21, 2012 10:18 am

I think i,'ve somewhere that these shocks were supplied by the amc owners club

Nostromo
Posts: 44
Joined: Sat Jun 23, 2012 5:40 pm

Re: G12 rear shocks

Unread post by Nostromo » Sat Jul 21, 2012 1:05 pm

Hi - Thanks again all for your replies.

@DAVE M2 - Thanks for the manual - some useful stuff in there I don't have in the others I've been able to find on the interwebnet so far. However as you suggest, the shocks it covers are the just the sealed units.

@The Mighty Gusset - Thanks for the info - btw - don't be distracted by the pretty red colour - I did that - they used to be black!

@Hooli - Ta - points noted.

@livinginthepast - interesting - just registered with the AMC forum and asked - thanks

Ian

Nostromo
Posts: 44
Joined: Sat Jun 23, 2012 5:40 pm

Re: G12 rear shocks

Unread post by Nostromo » Sun Jul 22, 2012 4:16 pm

Well it seems like I'll be doing the suck it and see thing as no one (that's replied anyway) over on the AMC forum has come accross these particular puppies before either. Once again thanks for your input gents.

Before I go though Mr. Gusset I had to chuckle at this one...
The Mighty Gusset wrote:For oil viscosity he experimented with dropping things into different oils and decided that SAE 2.5 was probably ideal, but as he didn't have any, decided to settle on some SAE 5 synthetic fork oil that he'd scored cheaply off Fleabay.
I love it - he first did careful analasys until he came up with an optimum solution... Then said fcukit - this is cheap - I'll use that - arf - good man!

Thanks

Ian

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