Can anybody help me. I am restoring a prewar Norton which was fitted with a sidecar and the front forks are set up to give a reduced trail for the sidecar. I am interested how this is achieved. I noticed on this site that the normal 16H top links are pt. nos.3191 & 2 same as those quoted in the civilian parts list from 1933/4. The W.D.Big 4 the top links are part nos 2259 & 2260 are these dimensionally different ?. I would have thought the distance between the spindles on the Big 4 should be less in order to reduce the amount of trail for sidecar work. I can find no record for Norton listing alternative links to modify the trail for sidecar work, other than those listed in the W.D. Big 4 parts list on this great website. Can anybody confirm the spindle centres for both of the top links mentioned. For I believe my bike was fitted post war with top links of a W.D.Big 4 to give the sidecar trail.
I am sorry to say I can not (yet) tell you the difference.
You are correct in your finding that only for the military B4 there is a different spare part number.
Civilian bikes all had the same spare parts numbers.
I have not come around to finding all the differences between the B4 and 16H but will do in future.
I hope to be able to get the dimensions soon and will let you know if still needed.
I have had a discussion with Lex Schmidt about it and he told me that a search he did with other B4 owners did not lead to a positive identification of differences between actual parts.
It is therefore believed that despite the spare part number difference there is no proven difference in the actual parts.