Gearbox spotter's guide?
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Gearbox spotter's guide?
I need to buy a new case for an AMC gearbox (1958 AJS 18CS), thanks to a damaged mounting lug.
eBay provides, but some of the vendors aren't sure if they're selling Burman or AMC cases. Is there an easy way to tell from photos?
From my research, it looks like the Burmans consistently have mount lugs that are cylindrical, with cast-in supports leading to the case. The AMCs have ears that smoothly integrate into the case (the mount has a triangular profile) and one of the AMC mounts will have a hole cast into it.
Is this a reliable indicator for such things?
While I have you, two other questions:
-at least one vendor is selling a case with a mount that has been machined down to be 82 mm wide. Is this normal, is it presumably done to re-fit to a different bike, and is it safely correctable with a spacer?
-anything I can look for or should look for in assessing these cases? Is there a known weak spot where they crack?
(My current transmission is intact and seems to work fine, but part of the front mount was destroyed, probably by some motocross activity back in the day. I'll be transplanting the guts and outer covers into this new case)
eBay provides, but some of the vendors aren't sure if they're selling Burman or AMC cases. Is there an easy way to tell from photos?
From my research, it looks like the Burmans consistently have mount lugs that are cylindrical, with cast-in supports leading to the case. The AMCs have ears that smoothly integrate into the case (the mount has a triangular profile) and one of the AMC mounts will have a hole cast into it.
Is this a reliable indicator for such things?
While I have you, two other questions:
-at least one vendor is selling a case with a mount that has been machined down to be 82 mm wide. Is this normal, is it presumably done to re-fit to a different bike, and is it safely correctable with a spacer?
-anything I can look for or should look for in assessing these cases? Is there a known weak spot where they crack?
(My current transmission is intact and seems to work fine, but part of the front mount was destroyed, probably by some motocross activity back in the day. I'll be transplanting the guts and outer covers into this new case)
1958 AJS 18 CS (a work in regress)
Ongoing rebuild photos: https://www.icloud.com/sharedalbum/#B16GWZuqDGvT59n
Ongoing rebuild photos: https://www.icloud.com/sharedalbum/#B16GWZuqDGvT59n
- dave16mct
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Re: Gearbox spotter's guide?
If you're looking at the rear part (main) of the shell, there will be 5/16" studs protruding which hold the inner cover. Burman covers are held with 1/4" whitworth screws. Also the AMC box outer has an oval inspection plate held on with 2 2BA screws. The Burman inspection is round with a large screwdriver slot and just screws on. Be carefull not to buy an AMC case from a Norton. Also this another way to identify the box, Matchless and AJS serial numbers start with an 'M' Norton starts with an 'N' (the lugs are in a different place) Burman numbers usually start with 'GB' More about numbers here:
http://archives.jampot.dk/technical/Transmission/
Cheers Dave.
http://archives.jampot.dk/technical/Transmission/
Cheers Dave.
- thornebt
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Re: Gearbox spotter's guide?
As far as identifying whether it's AMC or Burman I think it's as simple as the AMC gearbox has an oil filler cover with two screws fixing it and the Burman box has a large slot in it. Cheers. Bruce.
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Re: Gearbox spotter's guide?
The usual reason for reducing the mounts on a AMC gearbox is to fit it into a norton featherbed frame to create a Triton.
- Peter Morris
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Re: Gearbox spotter's guide?
AMC Gearbox
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- Peter Morris
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Re: Gearbox spotter's guide?
Burman Gearbox
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- robcurrie
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Re: Gearbox spotter's guide?
Peter's photo of the AMC gearbox is a bad example, it is the Norton version. The AJS/Matchless version has a cutout in the top mounting for the adjuster.
Rob C
Rob C
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Re: Gearbox spotter's guide?
As well as the Burman GB 'box in Peter's photo there's also the Burman CP 'box fitted to AJS and Matchless bikes and which preceded the Burman GB type up to around 1950 'ish.
This one is from a 1947 Ajay Model 18............
This one is from a 1947 Ajay Model 18............
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'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
- sjr
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Re: Gearbox spotter's guide?
I have a genuine AMC case which is surplus to requirements. Please send me a PM if interested. Happy to send you some photos.rcousine wrote:I need to buy a new case for an AMC gearbox (1958 AJS 18CS), thanks to a damaged mounting lug.
eBay provides, but some of the vendors aren't sure if they're selling Burman or AMC cases. Is there an easy way to tell from photos?
From my research, it looks like the Burmans consistently have mount lugs that are cylindrical, with cast-in supports leading to the case. The AMCs have ears that smoothly integrate into the case (the mount has a triangular profile) and one of the AMC mounts will have a hole cast into it.
Is this a reliable indicator for such things?
While I have you, two other questions:
-at least one vendor is selling a case with a mount that has been machined down to be 82 mm wide. Is this normal, is it presumably done to re-fit to a different bike, and is it safely correctable with a spacer?
-anything I can look for or should look for in assessing these cases? Is there a known weak spot where they crack?
(My current transmission is intact and seems to work fine, but part of the front mount was destroyed, probably by some motocross activity back in the day. I'll be transplanting the guts and outer covers into this new case)
Regards
Steve
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Re: Gearbox spotter's guide?
Ah! Is that cutout in the top mount a decisive indicator it's an AJS/Matchless box?robcurrie wrote:Peter's photo of the AMC gearbox is a bad example, it is the Norton version. The AJS/Matchless version has a cutout in the top mounting for the adjuster.
Rob C
1958 AJS 18 CS (a work in regress)
Ongoing rebuild photos: https://www.icloud.com/sharedalbum/#B16GWZuqDGvT59n
Ongoing rebuild photos: https://www.icloud.com/sharedalbum/#B16GWZuqDGvT59n