Chain case repair and query

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Chain case repair and query

Postby asterysk_usa » Mon Nov 11, 2019 2:46 pm

Well I found the oil leak source ! the round boss part has partially separated from the back piece ( green arrow ). Probably should have had a closer look after blasting and before priming ! Is this a brazing job ?

Also wondering what the metal flange was for ( red circle ) , it is well bashed about but I’m sure it had or has a purpose

Are these back plates easy to come by ?

Image

Edit: After uploading I saw that the photo has a bit of an optical illusion , it is actually looking inside the back plate and if you stare long enough you will see it magically appear dished inwards, however on first look it appears to be the outside


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1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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Re: Chain case repair and query

Postby Greybeard » Mon Nov 11, 2019 3:01 pm

Your mention of optical illusions reminded me of this TV clip, which whilst probably well known to UK folk, may be new to you ;)
Sorry it doesn't answer your query but it might provide some amusement.

Steve


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Re: Chain case repair and query

Postby cfaber » Mon Nov 11, 2019 3:07 pm

That flang is a catch to grab oil slung up by the primary chain and divert it onto the dynamo chain. Yours is badly damaged, it should look like a U channel which tapers down towards the dunno chain
Fix it until it's broken!

Otherwise how will
anything get done?

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Re: Chain case repair and query

Postby asterysk_usa » Tue Nov 12, 2019 3:55 am

cfaber wrote:That flang is a catch to grab oil slung up by the primary chain and divert it onto the dynamo chain. Yours is badly damaged, it should look like a U channel which tapers down towards the dunno chain


Does anyone perhaps have a photo showing how this this "catcher" should look like , the part number for my 18S is 013679 (chaincase back-half)
1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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Re: Chain case repair and query

Postby alanengineer » Tue Nov 12, 2019 8:24 am

The 'round boss' should have a bit of slide in it to accommodate gearbox movement, so you will never get it fully oil tight.
the shape of the rim of the chaincase should be smooth and uniform, yours shows quite a kink above the dynamo hole. when laid flat should be a good fit with no gaps, that a potential oil leak.

They do come up regularly and not a huge price, so sit back and wait for a good one. If you are good with a forming tool (hammer) its fixable

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Re: Chain case repair and query

Postby robcurrie » Tue Nov 12, 2019 12:43 pm

asterysk_usa wrote:Does anyone perhaps have a photo showing how this this "catcher" should look like , the part number for my 18S is 013679 (chaincase back-half)

This is the closest I could find.

Rob C
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Re: Chain case repair and query

Postby SPRIDDLER » Tue Nov 12, 2019 2:16 pm

alanengineer wrote: the shape of the rim of the chaincase should be smooth and uniform, yours shows quite a kink above the dynamo hole. when laid flat should be a good fit with no gaps, that a potential oil leak.
They do come up regularly and not a huge price, so sit back and wait for a good one. If you are good with a forming tool (hammer) its fixable


Chaincase interior snip.JPG


It's new unused stock and on eBay now for £85. https://www.ebay.co.uk/itm/Matchless-AJ ... Sw7qRdvb2c

(Being sold by 'ITMA' whom some may remember from these Forums ;) )
Fit the chaincase with the 'new' design club seal: http://www.amoc-parts.com/store/comersu ... duct=23441



The 'round boss' should have a bit of slide in it to accommodate gearbox movement, so you will never get it fully oil tight.

This gives an idea of the clutch shaft oil baffle arrangement although I'm not sure whether it was a factory fitment on all 50's chaincases, my '54 has never had one....
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Last edited by SPRIDDLER on Tue Nov 12, 2019 10:32 pm, edited 1 time in total.
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Re: Chain case repair and query

Postby ajscomboman » Tue Nov 12, 2019 3:25 pm

To clarify, the case with the circular deflector around the mainshaft was in use up to 1955 and it was fixed in position. The later sliding seal type in Spriddlers illustration was from 1956-57. It's a far better design and can be retro fitted to earlier models. There is however a very successful mod that can be carried out to the earlier case that help prevent the ingress of water and the escape off oil and can be carried out on road models. A dished competition deflector plate can be fitted between the gearbox sprocket nut and sprocket, and on the rear of the case either a felt or leather washer can be fixed with contact adhesive.

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Re: Chain case repair and query

Postby Andy51 » Wed Nov 13, 2019 10:22 pm

Slightly off subject, but where does one get one of these dished competition deflector plates? I have a '54 18S and would like to improve the primary chaincase sealing. I have suffered from water ingress, turning the oil to mayonnaise, and although the chaincase seal does not leak, I still lose oil from Dynamo or gearbox orrifices. Cheers, Andy

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Re: Chain case repair and query

Postby asterysk_usa » Thu Nov 14, 2019 3:20 am

ajscomboman wrote:To clarify, the case with the circular deflector around the mainshaft was in use up to 1955 and it was fixed in position. The later sliding seal type in Spriddlers illustration was from 1956-57. It's a far better design and can be retro fitted to earlier models. There is however a very successful mod that can be carried out to the earlier case that help prevent the ingress of water and the escape off oil and can be carried out on road models. A dished competition deflector plate can be fitted between the gearbox sprocket nut and sprocket, and on the rear of the case either a felt or leather washer can be fixed with contact adhesive.


Thank you for the clarification, I have been scratching my head trying to work out how the circular deflector was meant to move !

I will keep an eye out for the later sliding version, I am on a mission to have an oil free floor (and I would also like to stop global warming )
1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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