Lightweight rear suspension units

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
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Lightweight rear suspension units

Postby Roderick » Fri Jan 20, 2012 7:42 pm

Is spring strength the only difference between the 250cc & 350cc rear suspension units? Can you tell the 2 types apart looking at the outside? Are the 350cc units, for example, longer? Can they be replaced with modern units? Has anyone done it? It looks as if the bottom clevis might be able to be unscrewed.

The parts book indicates that the 2 models have different swingarms (presumably the 350cc's swingarm is longer?) & the 350cc has 18 in.rather than 17 in. diamter wheels but both models share the same rear subframe which indicates that the 350cc rear suspension unit might be longer. Anyway, I can't find answers in the archives, etc. Anyone knowledgeable on this subject out there?

Incidently, I'm finding rebuilding a 350cc Lightweight from a basket to be a bit more of a challenge to the old brain box than rebuilding a straight forward AMC twin & my first ever motorbike in 1968 was 1961 AJS 250 Lightweight!
Rod

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Lightweight rear suspension units

Postby Don Madden » Fri Jan 20, 2012 8:00 pm

My Girling catalog gives G2; 14.9in extended length & spring of 8.0in long, 110lb rate. G2CS: 15.8 long, spring 8.0 & 90lb. G5: 15.3 long, spring 7.4 & 100lb. AJS models equivelent. My Hagon catalog does not list AMC bikes except for the Stormer series but I suspect they can provide units to suit any bike. Cheers, Don.

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Lightweight rear suspension units

Postby cbranni » Fri Jan 20, 2012 8:25 pm

Not sure if I can help but I too have looked in the spares books and the springs have different numbers so too the inner member, so common sense says they are not the same, only thing can be the overall length and the spring rating, but they both have same swinging arm and rear frame
My two lightweights (250 and 350) are in winter storage 15 miles away, I could go check out the overall length on both if that helps.
Colin

Don done his magic again........a fountain of information


Edited by - cbranni on 20 Jan 2012 8:26:54 PM
only dead fish go with the flow

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Lightweight rear suspension units

Postby Roderick » Sat Jan 21, 2012 12:12 pm

Many thanks, Don & Colin, that's all I need to know!
Rod

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Lightweight rear suspension units

Postby John Jarrett » Sun Jan 22, 2012 6:30 pm

Don,
You obviously have access to an old Girling catalogue.... not somethin I have ever seen. Any chance that you could share the numbers of the suspension units for the various lightweight models? Also, is the length you quote eye to eye centres or overall unit length top to bottom?
Many thanks
John

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Lightweight rear suspension units

Postby Don Madden » Sun Jan 22, 2012 10:16 pm

I do have an old Girling catalog. G2: Compl unit 3911, spring 9044/277; G2CS: 4000, 9054/58; G5: 4163, 9054/53. Most vendors specify length eye-eye but Girling did not say. Cheers, Don.

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Lightweight rear suspension units

Postby BigAl350 » Tue Jan 24, 2012 3:03 pm

I replaced my completly-knackered original rear shocks on my 1960 AJS Model 8 when I got it back on the road about three years ago. I used this chap: http://www.njbshocks.co.uk

He is a British bike owner and has/had a Matchless G5 himself. Helpful, pleasant and the gas shocks supplied were about £100 - more expensive than some but they give an excellent ride with my 130kgs on the bike. BUT - they are NOT adjustable - the originals were. Some may find them a little hard for normal riding but they do damp nicely!

After being on the bike for three years - and it lives outside and is used almost daily, year-round - the NJB shocks are still in very good order but I do spray them with an anti-corrosion agent.

No clevis on any of my 3 Lightweights by the way.

You could also try Hagon - they can make up nearly anything and can customize the shocks to you and the bike.

BigAl


Edited by - BigAl350 on 24 Jan 2012 3:03:36 PM

Edited by - BigAl350 on 26 Jan 2012 1:33:37 PM
Al Bolton, G4VSQ
1960 Matchless G5 (Off the road for now, maybe for sale?)
1960 AJS Model 8 (Just passed MoT)
1962 AJS Model 8 (Still lurking in a Devon shed in bits)

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Re: Lightweight rear suspension units

Postby Roderick » Mon Oct 26, 2015 6:02 pm

The length eye - eye for Lightweight 250 & 350 rear suspension units is 14 & 3/4 inches and 15 & 1/4 inches respectively. I have measured this on a pair of unmolested 250 and a 350 frames which I have owned since 1968 & 1971 respectively, i.e. well before the classic bike era caught on & I am pretty sure both frames are unmolested originals.

Unfortunately, the extended lower section of the Lightweight rear suspension unit (carrying the bottom eye) does not seem to unscrew as does the Heavyweight Girling rear suspension unit. It seems to be brazed or welded together with the main section. There's little to indicate, however, exactly what was done & how.

The Lightweights are such tricky machines to rebuild, apparently similar but often not so, e.g. the rear bottom frame (the pressed steel channel with the exhaust system bracket which differs by being longer on the 250 to accommodate the smaller wheel & mudguard. Not obvious!

Rod

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Re: Lightweight rear suspension units

Postby clanger9 » Tue Oct 27, 2015 12:54 pm

I spent a while looking for suitable replacements for my G2 (hint: not easy!), only to find that my knackered-looking original rear shocks were completely serviceable and leak free.

At the time, I spoke to someone very helpful at http://www.bike-revival.co.uk/ - they couldn't exactly match the AJS units, but did suggest 390mm Betor MX progressive shocks or 400mm MDI Trail units with 100lb springs. Those would probably work well (and look OK) on a CS. The big challenge is finding something that will clear the chainguard (if you have one fitted).

In the end I found my shocks just needed a clean up and new covers; I hadn't realised that these are easily removable and widely available. Now they work properly & look like new. :)
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: Lightweight rear suspension units

Postby Ozmadman » Tue Oct 27, 2015 1:52 pm

That's what I did with mine, repainted with new chrome sleeves
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Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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