This listing is for the distinctive coarse thread, curved head filler plug fitted to Norton upright gearbox's on the front cover from the early 1930's to 1950. These are CNC stainless steel, with polished head and we offer 3 types - Road models, Inter and Manx lockwired type and wasted racing type.
Price is each
Background and types Information:
The upright Norton gearbox was first introduced in the early 1930's to replace the similar looking Sturmey Archer type gearbox's fitted before then. This gearbox was filled with oil by means of a coarse threaded plug situated on the lower left part of the front gearbox cover. As well as its coarse thread (only used on this type of plug), the original nuts had a distinctive shoulder - and this was designed to fit on a similar flat face on the cover (and although many people try to fit Red Fibre washers over the plug to prevent leakage - a washer was not originally fitted).
The original bolt also had a distinctive slightly curved head - of the design distinctive to many Norton bolts of the 1930's - 1950's era.
Postwar the upright gearbox design was modernised on road going models, first in 1946, with a round clutch worm inspection cover, then again in 1947 with an oval type inspection cover, which remained until the introduction of the 'Laydown' gearbox on most road models, in 1950. However, the Gardengate Manx models and 500T trial models conitnued to use the pre-war 'Dollshead' type upright gearbox all the way through their life postwar (i.e. until introduction of Featherbed Manx). All these models were fitted with this type of filler plug.
We CNC machine these nuts, from original patterns, in three different patterns - but rather than the dull plated and slightly rough finished original Norton item, we manufacture them in stainless steel -- and then linish and polish the head, so as well as being practical, they also look very pretty, as they are positioned in a prominent position.
0998_1 is the standard type: fitted to most roadgoing models, and is finished to the same dimensions
0998_2 is the Manx/Inter type: these are just as the normal type - except they are drilled to be lockwired - an essential requirement for any competition bike, to avoid oil spillage on the track. Although not strictly necessary on a road bike, it is a useful addition, as lockwiring can prevent accidental loss of the gearbox filler nut if not fully tightened. It also gives International SOHC models more of the look of its racing heritage. An original Manx filler plug is shown in the pictures, alongside our version
0998_3 is a 'Wasted' Manx type: This is not an original Norton feature, but was a very common modification of this nut on many racing motorcycles - as this nut can be considerably lightened by drilling its centre. I have seen this done on many genuine 1930's Inter's and Manx's and normally did it on my own competition bikes - it is in the style of Francis Beart, if you like! We take the 0998_2 version as the starting point, but then have an additional CNC cycle to bore the bolt and shape the curve of the head, before polishing, to give it a very pretty look. Personally, I think as well as being practical for competition, it enhances the look of the bike. (sorry not cheap, but additional CNC op requried to produce these)
Update July 2021: We will also shortly be adding the drain plugs for Norton gearbox's, which were also produced in more than one variation. If you have a Sturmey Archer original pattern filler plug - providing you can give dimensions, we may also produce a batch of those in the near future. Please email firstname.lastname@example.org