I've decided to fit a damper to my B'Zuki toi help control the shakes(!). I've bored the steering head adjuster and bought a damper complete from my local British Bike shop which is a Wassell item designed for an A10 / B31. This is a nicely made item. Obviously I will need to modify or remake the retaining plate that fits to the frame, but what puzzles me is what stops the castellated nut and hence the pressure plates from rotating relative to the bottom yoke. There are no tabs etc: the plates are merely discs with tabs to engage with the serrated nut.
Can anyone with a damper fitted to an A10/B31 help? The only possibility I can see is to glue the top plate to the underside of the bottom yoke with JB weld but would prefer something more robust.
This is the damper assembly:
(https://www.iansoady.org.uk/BSA/images/damper.jpg)
The big plate goes in the middle of the stack and bolts to the frame (with a sliding fit). A friction plate goes above and below it then the large discs that lock onto the nut with the keyways. On an A10 or B31 the bottom yoke has keyways to match so that nut pulls up into the yoke. That's the bit of the puzzle you are missing. If the hole in the steering head tube is big enough to clear the nut then you may be able to make an adaptor. Check the bottom yoke just in case its already machined.
This shows the machining in an A10 bottom yoke.
Great both, that shows where the tangs on the top plate engage. I'll have to think of a creative solution. The hole through my bottom yoke is too small for the nut. I could make a thick disc with a hole and those tangs to fit the nut but still need to find a way yo attach it to the yoke.
But that gives me something to work on.
If you have the patience of a saint you could mark out the yoke and file the shape. It would not need to be that accurate.