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Gearbox sprocket nut

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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.

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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.

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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. 

 


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