English French German Italian Spanish

Commando Gearbox

Submitted by antony_wass on Tue, 09/02/2021
Forums
Commando

Morning All, I am progressing with a 1972 Norton Commando rebuild (mainly from parts that i have acquired). I noticed yesterday evening that the gearbox that I thought that had planned for the project might well be unsuitable. The casing has a 'G' prefix. I think it should have a 'N' prefix?

If this is correct, do i need to source a replacement or just casing only? Thanks for your thoughts, suggestions and advice in advance.

Kind regards Antony        

Submitted by martin_freeman on Tue, 09/02/2021

Permalink

Dear Antony,

couple of things for you to check.

Does the gearbox fit in the engine cradle, lugs come I believe in different widths, too narrow and you could pack with washers.

Secondly does the gearbox have a commando mainshaft? easily recognisable as it is threaded right to end and has a circlip groove in splined section for clutch to locate on. If unsure post a picture of end of mainshaft. While examining that end of box look for any cracks in casting between mainshaft bearing and layshaft bearing as that area is a known weakness and reason why original case may have been swapped.

Good time to be spannering if inside, I have commando engine on my kitchen table at moment, while snow gently settles outside.

Regards martin

 

 

Submitted by dan_field on Tue, 09/02/2021

Permalink

N and NA are usually Norton Boxes, M and MA are Matchless which have pretty much the same internals but the cases are different and not easily interchangeable, although you can put the Matchless internals into a Norton case. I may be wrong but I think G and GB are AJS gearboxes and the G was the earlier Burman type box but might be wrong?! Maybe someone else could shed some light? 

Dan 

 

 

 

 

 

 

Thanks for your thoughts Martin, yes it does have a commando main shaft, thread and circlip and was used in my other hybrid Norton featherbed commando sandwiched between alloy cradle mounting plates and using standard commando primary chain case, hence the reason for assuming that it was a Norton box. Done a little measuring tonight and too wide across the lugs, measured about 89mm vs cradle 82mm. However the main problem is the gearbox hole centres that look way too small for the proper commando cradle. Back to the drawing board I fear for me!  Hope you managed to make some good progress with your own engine work, you definitely have the right idea tucked up in the warmth of the kitchen on a day like this! 

Submitted by dan_field on Tue, 09/02/2021

Permalink

If the holes are two small as well as being in a different place then I’d say it was a Matchless/AJS box as they have smaller mounting holes. Can you post a picture? My ES2 had an AMC box fitted but it was machined to make everything fit/line up. Although it caused clutch clearance issues.

dan 

 

 


Norton Owners Club Website by 2Toucans