Hello Martin,

Engine sprocket nut can be loosened by holding the sprocket firmly and loosen the nut. You can hold the sprocket by a piece of chain around the sprocket and clamp the chain in a vice.
Easier would be to fix a piece of chain to a rod and then sling the chain around the sprocket. That should give enough "support" to loosen the nut.
(Some car oil filter removal tools look similar).

Cheers,

Rob

thx a lot for you posting, rob.
sounds sensible, i will try it as suggested.
i hope my questions dont sound too stupid. i am quite familiar with harleys, moto guzzis or old jap bikes. but the old war horse is my first brit bike and thus i want to avoid beginner's mistakes.

An air tool will often shock nuts on rotating parts loose without turning the component if you struggle to hold it.

The clutch pullers are not complicated and should be available from any Norton parts source. They are used on all post-war pre-Commando models.

RGM certainly lists them.

http://www.rgmnorton.co.uk/buy/clutch-puller-for-amc-gearbox_1047.htm