Speedo drive

When I got this bike the speedo was disconnected and stripping the front wheel showed that the drive unit needed restoration. The biggest problem being that the drive dogs were worn or absent. I was able to restore these by welding on tabs but this was at best a temporary repair and in the long run I'd always expected to fit a new drive. I eventually ordered one and fitted it. I had expected it to fit immediately but I was surprised in that the new drive teeth only barely contacted the hub even when the axle was tight. 

New speedo drive in position, drive dogs barely enter the driving slots in the hub.

I had initially attributed this to an error in reassembling the hub: you will recall that it's not really possible to control how much of each bearing cone screws into the central tube and thus how much of each protrudes on each side. I had tried to adjust my refit to suit my old speedo drive and hadn't realised that the speedo is itself adjustable to fit the bearing cone. This was because my original, being severely worn, had already been adjusted to the maximum and all adjustment washers had therefore been removed! For this knowledge I thank the Fb NSU group. 

The new speedo drive comes with three spacer washers internally below the white foam disc.

Speeedo drive adjusting washers beneath the foam seal. One washer removed, 2 left in situ.

Removing one washer allowed the drive to fit nicely against the bearing cone and yet still mesh the drive teeth with the hub slots. This looks fine now but I will see how it beds down in use and possibly remove another later.

Dogs fit better into driving slots