As Ray says, there is no rubber washers shown in the late war parts lists. I can't actually think of any other WD bike that has a rubber mounted regulator? Ron

email (option): ronpier@talk21.com

Thanks Ron. The set up in your photo is the same as an original, seized up mudguard I have. Two's only a coincidence, but it makes more sense now. I initially assumed that the locknuts in my 1940 parts list referred to those holding the regulator box. However, seeing that these are the thinner nuts makes sense: they fix the bolts to the mudguard, before the reg box is fitted (with or without rubber washer between).

Ian, I was looking closely at the photos I have collected today (trying to narrow down the various crankcase shields) and came across a good period shot of a voltage regulator fitted to a bike - a detail I hadn't noticed before.

This is a brand new M20 that has just had the original C number painted out with the Australian ARN number. Unfortunately that number is somewhat obscured but given the dozens of other bikes in the photo it is most likely from C910.

This clearly shows an unpainted nut holding the regulator tab and what really does look like a rubber spacer but that isn't clear enough for a guilty verdict.

It won't impact world hunger but an interesting data point nonetheless.

email (option): rays54@hotmail.com

Am away for a few days now - but will send photos of reg mounting studs I have now found on 2 different mudguards
These were a one piece design with threaded studs either side
In the centre / there was a flat section where a spanner could be used to hold while tightening the nuts top or bottom end

These were fitted to later guards & I suspect these were a war time economy measure

Job

email (option): jonnyob1@googlemail.com