Speedo drive mashed

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Speedo drive mashed

Postby Oggers » Sat Mar 02, 2019 5:33 pm

DSCF3011.JPG
I was all going so well....then as per pic, and I have no idea why it happened! Looks like the speedo drive casing has just disintegrated in the centre. It has come well away, exposing the gear which drives the worm on top. It also sheared the drive cable, and I hope not wrecked the speedo itself.

Some Qs if I may

Any idea what happened here?
Is it a known fault?
I assume spares are readily available?

Also, as part of the shake down post rebuild - rebuild by PO I hasten to add, it is leaking far too much oil at the top of the valve drive cover, also from underneath somewhere and maybe even the pressed steel primary chain cover - cannot be absoulutely sure. Oh well...It'll keep me busy I supoose....
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Re: Speedo drive mashed

Postby dave16mct » Sat Mar 02, 2019 5:47 pm

The usual cause is incorrect assembly of the oilseal retainer in the hub. Have a look at posts on speedo drive lock-up. There's a cut-away view of the assembly in the Tech articles.
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Re: Speedo drive mashed

Postby Mick D » Sat Mar 02, 2019 5:53 pm

Hi Oggers

Your speedo drive failure smacks of incorrect assembly, (order or torque), you will need to strip it down carefully and document how it was assembled to allow us to comment with certainty. The speedo drive assembly is a known area where others have experienced failures.

Have you had the back wheel off since you have owned the bike?

It's fixable and the speedo should be OK

Regards Mick

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Re: Speedo drive mashed

Postby Oggers » Sat Mar 02, 2019 6:03 pm

Gents

Many thanks for the replies. Not touched the rear wheel at all since purchase. I will strip it down and revert. Spares OK? Do I go to AMC spares or similar, or chance EBay? If the latter, what description am I looking for - as I guess drives may be compatible with other bikes?

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Re: Speedo drive mashed

Postby Mick D » Sat Mar 02, 2019 6:13 pm

Hi Oggers

Strip it down first - the speedo drives can be serviced and a second hand item may suit your replacement parts needs - failing that I'd go for a recognised supplier. I think you'll find the part number / details of the drive on the grease seal cover plate fitted to the inner face of the GB.

Not a good photo but it should give you a pointer of where the detail may be:

Speedo Drive.png


Regards Mick
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Re: Speedo drive mashed

Postby clive » Sat Mar 02, 2019 7:49 pm

The drive unit in Oggers photo is the earlier type with the flat end. This may not have the part number and ratio in the place in micks photo. However all our postwar bikes have a 2:1 clockwise drive.
Incidentally whilst i think many of these failures are as described, incorrect assembly, i also believe a worn out drive worm gear can lock against the drive ring. The disintegration of your unit is pretty catastrophic and there appears to be damage along the top of the drive unit. Usually when its the wrong assembly the unit locks up the rear wheel bearing rather that disintegrating.
clive
if it ain't broke don't fix

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Re: Speedo drive mashed

Postby ajscomboman » Sun Mar 03, 2019 10:07 am

Oggers wrote:Gents

Many thanks for the replies. Not touched the rear wheel at all since purchase. I will strip it down and revert. Spares OK? Do I go to AMC spares or similar, or chance EBay? If the latter, what description am I looking for - as I guess drives may be compatible with other bikes?


May I be so bold as to suggest that, as you've had so much help and advise that you join the club and buy the spares from our parts service.

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Re: Speedo drive mashed

Postby Oggers » Sun Mar 03, 2019 10:42 am

May I be so bold as to suggest that, as you've had so much help and advise that you join the club and buy the spares from our parts service.


You may indeed Sir. Duly paid 28 GBP by Paypal.........

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Re: Speedo drive mashed

Postby ajscomboman » Sun Mar 03, 2019 10:59 am

Oggers wrote:
May I be so bold as to suggest that, as you've had so much help and advise that you join the club and buy the spares from our parts service.


You may indeed Sir. Duly paid 28 GBP by Paypal.........


Thank you, you're a gentleman. :beer:

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Re: Speedo drive mashed

Postby clive » Sun Mar 03, 2019 3:43 pm

Oggers wrote:
May I be so bold as to suggest that, as you've had so much help and advise that you join the club and buy the spares from our parts service.


You may indeed Sir. Duly paid 28 GBP by Paypal.........

Welcome to the club.
clive
if it ain't broke don't fix

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