Tank & seat mounting

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Plumsteadboy
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Tank & seat mounting

Post by Plumsteadboy »

Hi,
I have recently aquired a AJS CSR 650. When removing & refitting the petrol tank it struck me what an odd idea the rear clamp is. It's not only awkward to remove & refit, but also gets in the way of the throttle & air cables. Do any of you know why AMC didn't weld a bracket on the rear of the tank & use the threaded boss on the frame to fix to? I know they had problems with split tanks but can't see this type of fixing would makes things worse. I also think the method of seat mounting is rather crude to say the least when comared to my 650 SS.

Martyn.
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ajscomboman
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Re: Tank & seat mounting

Post by ajscomboman »

Plumsteadboy wrote:Hi,
I have recently aquired a AJS CSR 650. When removing & refitting the petrol tank it struck me what an odd idea the rear clamp is. It's not only awkward to remove & refit, but also gets in the way of the throttle & air cables. Do any of you know why AMC didn't weld a bracket on the rear of the tank & use the threaded boss on the frame to fix to? I know they had problems with split tanks but can't see this type of fixing would makes things worse. I also think the method of seat mounting is rather crude to say the least when comared to my 650 SS.

Martyn.
They did use a rubber band method after 1960 models which is the year of the tank you're talking about. That clamp was for that year only and was soon dropped for the reasons you mentioned.
Plumsteadboy
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Re: Tank & seat mounting

Post by Plumsteadboy »

Thanks ajscomboman. That would make sense, but where does the rubber band go?
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ajscomboman
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Re: Tank & seat mounting

Post by ajscomboman »

On the later tanks there are 2 welded top hat lugs at the rear of the tank. The band goes around one lug then under the frame tube and around the second lug.
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robcurrie
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Re: Tank & seat mounting

Post by robcurrie »

Welcome Martyn, there are 2 projections on the rear of the tank and the rubber band is hooked on one then taken under the frame below the tank, then brought up and hooked onto the other. There is also a moulded rubber block which fits on the frame and supports the rear of the tank.

It is time to introduce you to Christian's Archive which contains all the workshop manuals, parts lists and literature for AMC motorcycles, you will find it here:

http://archives.jampot.dk

Feel free to make a donation to help Christian keep this service going.

Rob C

Mr Swift lived up to his name and beat me to it!
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robcurrie
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Re: Tank & seat mounting

Post by robcurrie »

As an extra bit of info on this mounting, I used the correct rubber ring and block and they only lasted about 20 miles - the ring snapped and the block disappeared along with it. I have since made my own ring using tiedown bungee cord and in place of the block, I made up my own by bonding a few layers of semicircular rubber cut from soft rubber hose - the lower layer being slightly longer and strapped to the frame with cable ties.

Rob C
Plumsteadboy
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Re: Tank & seat mounting

Post by Plumsteadboy »

Thanks for the link. It's a real treasure trove of info.

Martyn.
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