Handlebar Diameters

The Spare Parts Lists are not a great help here, as they don't state diameters, but there are clues. Unfortunately, there doesn't appear to have been a list published for 1936 (when actually a lot of changes occurred) so we're looking at the lists marked 'Subsequent to 1933' and then 'Subsequent to 1937'. 

Taking as an example the valve-lifter lever, the part number 8794 remained unchaged for 1937 /1938/1939 (thus all production from September 1936 at least).

The 1936 brochure includes mention of the rubber-mounting system for the bars. In the illustrations, they look 1" to me. The 1937 brochure improvements do indeed state 7/8" so the best guess is that this change took place from the moment that production of the 1937 model year commenced after the works shut down during 1939 - i.e. September 1936 but it may well be that some before this were so fitted.  The brochures for 1938 and 1938 make no reference to handlebar diameter, and certainly not to any changes.

I suspect that matters have become blurred by the fact that the WD models (both 16H with the Trials Type, adjustable handlebars and SWD Big 4 which used the rubber mount) were fitted with 1" up until 1944 or so, at which point the War Office attempted to standardise all motorcycle controls at 7/8".

His next issue will be to find the U shaped metal bracket that keeps the 7/8 bars pointing the right direction when the rubber bushes are fitted. Also bars with the correct shape. Mine seem to be very old, and I assume original, but they start to curve too close to the end for the shoulders of the brake clamps to fit properly.

I think the bracket can be made from thin steel and I also think soft soldering would be OK. It doesn't work hard and there should be a big solder surface , but will that work on chrome? Nobody seems to make the proper ones. There cannot be a big market...

...also my old bar wall thickness is too great for a modern Halcyon bar end mirror to go in without attention on a lathe first...

Soft solder will not stick to chrome and I don't think would be strong enough. Brazing would be best because you can melt it away if the bars need to be changed but it's not good for the chrome. I had mine TIG welded on the little window at the back of the bracket. The heat discolouration is minimal and the weld can be painted because it is hidden by the top handlebar bracket.

Inter style bars with the U clip are listed on Paul Norman's Racing Norton website in both 7/8" & 1" variants. He also supplies the rubber "doughnuts" in both sizes. In the past Stu Rogers has supplied unplated bars with loose U clip, enabling you to position and braze (or tig) the clip before plating.

Ian McD