Hi
The top gearbox bolt (Dolls Head) on my 1938 Model 18 has the nut of the top mounting bolt on the RHS of the bike (and, to be clear, the head of the bolt on the LHS). It is very awkward to get at to allow adjustment of the primary chain. Is there a secret here ? Or, alternatively, should the top bolt be mounted the other way round so that the nut of the bolt is on the LHS of the bike ?
Head on the right and nut on…
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Gearbox Bolts
Norton supplied a special spanner(s) for the top gearbox nut. It is not flat in the traditional way, but offset to gain access. With this correct spanner I find adjustment is not a problem. The only problem is obtaining the spanner, as they are quite rare. Autojumbles or a wanted add might help. I have attached a photo of both types, the smaller spanner is the Manx version. Feel free to use the photo as required.
Barry Stickland
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Orientation
The wartime WD16H manual has a clear illustration. The nut should be on the drive side.Late-war (or possibly only post-war) nuts no longer had the reduced hexagon and thus require the larger spanner with cast markings shown in Barry's photo. From memory, with a "Doll's Head" box, the gearbox top bolt can be withdrawn with the positive stop mechanism in place, but it is a fiddle and requires removal of the domed nut on the rear. That said, how often must the top bolt be removed. The incorrect insertion is common, and presumably caused by building up complete boxes ans then attempting to fit.
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Hi, Richard's comment "The…
Hi, Richard's comment "The incorrect insertion is common, and presumably caused by building up complete boxes and then attempting to fit" is the probable answer I think because I had someone overhaul the gearbox for me last year.
Thanks for the photo Barry of the special spanner. As they are difficult to find I will make one of those by heating and bending a standard spanner. Could you give me the AF measurement please ?
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Gearbox Bolts
The larger size is 9/16 Whitworth, which is 1.010" (25.7mm) A/F
The smaller size is 7/16 Whitworth, which is 0.820" (20.8mm) A/F
Barry Stickland
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Head on the right and nut on the left on my pair. It's a lot easier to remove the gearbox end cover to extract the bolt than to remove the primary side.