Swinging arm mod, late G80CS

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
mdt-son
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Swinging arm mod, late G80CS

Post by mdt-son »

Fellows,
I was puzzled by spotting a swinging arm obviously taken off a 1967 G80CS which had forked shock absorber mounts. The complete forked mounts looked as if they were cast steel but as they were painted, I can't be sure. Now, the 1965 spares list amendment doesn't list a design change to the s/a. I looked at the image of another '67 which apparently didn't have forked mounts (proviso the s/a used on that particular bike was correct for that year). So, is this a clever homemade alteration or a late model factory change?

Greetings,

Knut Sonsteby
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Les Howard
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Re: Swinging arm mod, late G80CS

Post by Les Howard »

Hi. As far as I know, from 1963, the swinging arm on the heavy weight models had a welded steel plate with a single fixing for the suspension unit rather than a cast lug which was also a single fixing. Perhaps the swinging arm is from a Norton machine possibly a Featherbed model?. The Nortons used a cast forked bottom fixing for the suspension unit:

Les
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Les Howard
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Re: Swinging arm mod, late G80CS

Post by Les Howard »

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Rob Harknett
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Re: Swinging arm mod, late G80CS

Post by Rob Harknett »

G80CS Marksman was discontinued Aug. 1965. 1966 G85 CS Scrambler introduced, similar to G80CS new lighter frame, with more ridged rear sub frame, 7R type rear hub with 8 1/2 " brake. May 1967 G80CS Roadster introduced, similar to 1965 G80CS Marksman, but road trim, lights etc. This was short lived, discontinued July 1967. ????? Seems there was a change to G85CS, Then back to G80CS, could it be your G80CS has the G85CS type rear frame. Frame and engine numbers would help.
mdt-son
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Re: Swinging arm mod, late G80CS

Post by mdt-son »

Rob: Frame number C11361 and engine number G80CS/5386 (3rd digit was hard to read, I think they stamped a 7, then overstamped with an 8).
This makes it one of the very last G80CS made. The G85CS is all-braces, so no loose subframe. The swinging arm off the G85CS is completely different to the traditional AMC design.

Les: Thanks for the reference. It does resemble at the rear ends, however, the swingarm I looked at is definately AMC like. I will try to insert a few images tonight.

-Knut
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Re: Swinging arm mod, late G80CS

Post by 242017 »

I agree.....Its definately not a G85cs rear swinging arm.......it is though probably a " home made " mod...
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Rob Harknett
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Re: Swinging arm mod, late G80CS

Post by Rob Harknett »

1967 G80CS appears to end with frame C11555 3rd digit would have no real meaning what ever it is, last engine no. 5572.
The numbers look good for 1967 G80CS, anything odd about he bike must be custom made, or of something else non AMC
John Jarrett
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Re: Swinging arm mod, late G80CS

Post by John Jarrett »

The 1963 to 1967 G80CS (as distinct from G85CS which is completely different) did have a different swinging arm than the pre-63 frames and the road bikes of the 1964-67 era. AMC did away with the bottom alloy mount on the shock absorber and used a standard girling. The swing arm has a forked mount for the standard girling and is designed for AMC wheels, not Norton. From memory the width across the fork at the rear is slightly wider than the earlier swinging arm meaning that the wheel spacers are different. The mount to the front frame is standard AMC. I have a photo of this but for some reason, I get an error message that the file is invalid when I try to upload. I will try again when I have more time.
John
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Rob Harknett
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Re: Swinging arm mod, late G80CS

Post by Rob Harknett »

If you have a problem with the File upload John, email it to me prewar@jampot.com it may just be the file is too big.
Whatever, I have time to change the file so it will upload.
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Rob Harknett
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Re: Swinging arm mod, late G80CS

Post by Rob Harknett »

rear suspension b.jpg
Johns file attached he had problems with uploading, he e mailed it to me, it was about 10 x too large to upload here. I have cropped and reduced the file quite small, hope it is seen OK, Rob.
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