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slimline gearbox top bolt issue , 63 SS


The top bolt that secures the gearbox  is innacessible to a socket set.  The nut should be reduced hexagon to allow a socket to fit . But reduced to what?. Mine is 15/16 inch across the flats and needs a 1/2 inch whit socket  which fouls the box ., Is this some more foul play by Plumstead or just a PO  alteration?.  My 99 was no trouble ,but is not with me to check . Not clear what our suppliers are actually supplying but I think 7/16 whit  hex is needed ?.


The gearbox Top Mounting Bolt / Nut on a Dominator 88, 99, 650, 750 with AMC type gearboxes should be......

9/16" x 20tpi x 4 7/8" with a Reduced Hex Nut of 1/2" BSF (7/16" Whit) 

My King Dick 1/2 BSF socket fits this nut perfectly while allowing it to be turned by an extended bar.

I am not too sure if the Laydown Gearbox used the same Bolt / Nut set-up but my guess would be yes.


Thats  what i thought i should have (but dont ) , looking at the offerrings from RGM and Andover  its not clear what they are supplying , what do you think they mean ?.Thanks Phil, 


Robert.....the RGM & A/N Nut (p/n 15170) offerings will fit the bolt but whether you will be able to turn it to tighten is open to debate. All of my Dommies have used a reduced hex nut on this gearbox bolt.  I have tried the standard nut on the top bolt but the oil pipes get in the way of a spanner and a socket or box spanner does not have enough clearance to be used.



Thanks Phil, I think the best thing i can do is grind down the nut to a reduced Hex of  7/16 Whit. I am also thinking of scrapping the oil filter and annoying pipework !!. Never needed it on our other Nortons.


Hello again Bob and Phillip - I am just going to add my two-pennyworth.  I use an extended plug socket on that nut.  My socket fits the standard 14mm spark plug and the Bedford socket is stamped 13/16 inch  which is an AF size.  That came with my first ever set of spanners and sockets back in the sixties and it's still excellent.  The extended socket allows me to use a half inch drive Tommy bar or ratchet with a short extender to get the correct angle for tightening.  Keep taking the bills, both.  howard


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