I'm just about to tackle changing my gearbox sprocket, the first time I've done this job in 40 years (no, the sprocket's not that old—just a long time since I last had a Commando).
Can some kind soul save me some research and tell me what size spanner I need (presumably British Standard).
Not only have I forgotten the size, but whatever tool I used has vanished in the mists of time. Given that the nut's rather thin and surrounded by the dishing of the sprocket, I imagine that I may need to grind a cranked ring-spanner.
The gearbox sprocket nut needs 7/8 W/W spanner to undo or tighten it. This is the same size as the sump nut on most Dominator engines with a built in filter. The important point to note being the gearbox nut has a left-hand thread so is turned clockwise to release it whereas the sump nut has the more usual right-hand thread.
If you can find one the box spanner for these nuts is part number 12093 or 067624.
Very appreciative of this quick response—and for reminder about LH thread!
Under part number 06.7624 … n.b. for some curious reason AN list three different box spanners under the 06.7624 number:
plain 06.7624 for the 3/4+7/8 (G-BOX/FORK TOP & TO 1971 SUMP) (NM12093) (note the additional NM part number)
06.7624C for 1.1/2 X 1.5/16" (1972-1978 SUMP PLUG)
06.7624.1/4 for 1/4 x 3/16" WHIT (CYLINDER HEAD)
Note also the prices: £17.00 for plain 06.7624. To be fair, this on eBay ( Melco TW24 Whitworth Box Spanner 7/8 x 1 x 175mm (7in) MELTW24) is £15.58, albeit with free postage.
However, there are other respectable-looking second-hand offerings for less.