AJS & Matchless Owners Club

I have become mates with a C.N.C Programer, he has said he can write a program to produce a steel version of my rather week cast iron 1957 crank, dose anyone have access to the factory drawings for these parts? I have already looked on Christians archive, all to no avail.

I do not believe you will find a factory drawing, if you did, it may be of little use. These old drawing fade to almost nothing visible. You would probably do better using your flywheels as a sample. At least you will get what you want. I believe balancing / weight may also be needed. Not sure what year your G80 may be. There are number of drawings made by a pre war group member. With CNC programmes.

'A weak G80 crank'. is their such a thing.

alanengineer wrote:'A weak G80 crank'. is their such a thing.

Alan, I think it's more a case of 'the stronger steel one' vs the earlier cast iron flywheels and an increase in crankpin size.
There's a brief reference and rough drawing in Christians Archive:

http://archives.jampot.dk/editorial/Roa ... 0_and_500_(Motor_Cycle_Octo.pdf

I had a picture in my mind of a complete flywheel assembly. If it is just the crank pin, you are looking for, manufacturers show drawings and dimensions.
http://archives.jampot.dk/technical/Gen ... guides.pdf
There is one example, I have the full catalogue somewhere, but I think these pages are all there is for AMC.

I have a 46 G80 and I broke the crank pin on that and Malcolm Saggers fitted one of his big ends in that for me in the 90s and its been fine since. The pin that broke in the '46 G80 was a one piece repro pin where the 57 CS replica has a Two piece pin fitted by Alpha. I fancied manufacturing a crank which was long stroke and had a parallel press fit pin the same size as the O.D of the sleeve the original two piece design that way the standard rod and roller set up could be used. It was only an Idea I had and when someone offered to write the program for the manufacture of it for nothing it all of a sudden looked like a financially viable proposition. I might buy a pair of iron flywheels and use them as a pattern as I don't want to strip down an engine that works fine at the moment. thanks for your help and any tips would be gratefully received.

Did'nt Malcolm use BSA big end??

I am interested in this thread purely because back in the 1970's I replaced the crankpin and associated elements with a repro pin - can't remember where from. When I say "I" it was really done by a genuine expert, now unfortunately dead, using what appeared to be a professionally made massive arrangement of pins fitted at right angles into an even more substantial baseplate with an arrengement of guides to force the flywheels into precise conformity and if my memory holds up some work with "knife edges" and a soft mallet and a measuring device. It snapped after a few 1,000 miles and I sent the whole away to Alpha. After consulting with me they fitted what they referred to as an "oversize crank" and returned a complete carnk assembly to me. I just took their advice (I was hauling a sidecar and strongly made wood box at the time) and it's the same crank assembly now after quite a high mileage and being hard worked. No idea if they did any balancing work at all.

There was no up and down play of any form when I fitted the re-sleeved barrel and new standard piston. A little rock across the frame though not very much. I don't experience what seems to me extreme vibration but then I used to work the Matchless very hard and may just be accustomed to it. I started up this afternoon and when rev'd up to cruising throttle openings I am surprised at how well the pump returns oil to the tank. Perhaps in this respect I've been lucky.

I can't help wondering what's in there! When it gives up, will I be able to get it re-done? Did Alpha fit a BSA pin? What's the meaning of life, the universe and everything?

Just idle thoughts.

Johnny B

crank pin failure, now thats another story

I am now looking for a pair of 57-63 iron flywheels to use as a pattern, any offers?