55 / 56 crankshaft differences ?

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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5kids1dog
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Location: Nottinghamshire UK

55 / 56 crankshaft differences ?

Post by 5kids1dog »

Hi all,

I have a 1956 AJS 16MS that I pulled the top end off to cure an oil leak from pushrod tubes that has now seemingly turned into a full rebuild due to piston ring land warpage and a shot big end. So being on an extremely tight budget ive looked out for the decent crank to use , the bike came with a few spares including another crank that's stamped g3 on the flywheel.Ive bought very cheaply a g3ls 1955 bottom end with a good big end, but on examination the drive side axle is much shorter ( 1.5 inch as opposed to 3 inch ) can anyone shed light on this for me ?
It would seem its from a non cush drive version so maybe for a later AMC gearbox ?
See attached pics.
So my question is , can I use this in my crankcase and is it as simple as using a later sprocket and a cush drive center clutch ?
Any info or help appreciated.
Pics hopefully added!

Many thanks
Andy
5kids1dog
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Location: Nottinghamshire UK

Re: 55 / 56 crankshaft differences ?

Post by 5kids1dog »

SPRIDDLER
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Re: 55 / 56 crankshaft differences ?

Post by SPRIDDLER »

5kids1dog wrote: Sat Jan 27, 2024 4:44 pm Hi all,

I have a 1956 AJS 16MS that I pulled the top end off to cure an oil leak from pushrod tubes
Nowadays many of use 'O' rings instead of the rubber sleeve at the top of the p/rod tubes. The rubber sleeves became hard, brittle and leak.

Ive bought very cheaply a g3ls 1955 bottom end with a good big end, but on examination the drive side axle is much shorter ( 1.5 inch as opposed to 3 inch ) can anyone shed light on this for me ?
Bear in mind that the factory model year ran from Sept 1st to August 31st, not Jan to Dec so a bike first registered in e.g. Sept 1956 may be a 1957 model.
Does this tech info re drive axle changes help........?
Single drive axle change.JPG
So my question is , can I use this in my crankcase and is it as simple as using a later sprocket and a cush drive center clutch ?
I may be a bit befuddled with what dynamo/alternator/ignition/primary chaincase arrangement you have currently as the axle wasn't shortened until '57 but.....

How do you propose to drive the dynamo from the single sprocket?
If you intend to fit an alternator you'll need the alloy chaincase. There are various articles and threads on doing that but you need to be a subscriber to access them, view photos, use the 'Search' facility and to buy spares, (e.g the 'O' rings) from the club spares shop.

P.S. Ah, If you aren't a subscriber I don't think you'll be able to view my attachment so I've re-posted it below using a 3rd party host site........

Image
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Which taken at the flood............'
5kids1dog
Posts: 3
Joined: Wed Jul 05, 2023 4:41 pm
Location: Nottinghamshire UK

Re: 55 / 56 crankshaft differences ?

Post by 5kids1dog »

My bikes a 1956 16ms , sr1 mag and dynamo and the engine is stamped 56. The bottom end purchased is stamped 55 g3ls so that's where my dates came from. The bikes been modified into a scrambler style with 21 front wheel, completion ally top yoke, separate headlight and ally mudguards so not looking for originality . I'm not opposed to running the bike with no lights or charging system really. Just want to be able to use the thing. On my original crank the drive splines are damaged, on the spare that came with the bike the timing side is a smaller diameter so I'm guessing an earlier crank. On the purchased g3ls crank the timing sides same diameter but the drive side shorter. Just wanted to find info on front sprocket and if a cush drive clutch center is an easy fit, and required parts.
Thanks
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dave16mct
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Re: 55 / 56 crankshaft differences ?

Post by dave16mct »

It looks like a 57 crank in 55 cases. You'd need a 57 sprocket ( which has the dynamo sprocket) and an AMC clutch.
Dave.
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Re: 55 / 56 crankshaft differences ?

Post by SPRIDDLER »

5kids1dog wrote: Sun Jan 28, 2024 12:08 pm ............and if a cush drive clutch center is an easy fit, and required parts.
Thanks


Just to be clear, which gearbox do you have/intend using; an AMC or Burman B52? The longer axle with the shock absorber on your original axle will normally have been mated with a Burman B52 clutch and gearbox.
Here's a thread about fitting an AMC (cush drive) clutch to a Burman B52 'box........

viewtopic.php?p=183911&hilit=amc+clutch ... an#p183911
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Which taken at the flood............'
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