Is it too obvious to suggest that if all is well without the speedo drive,
then the problem HAS to be in the speedo drive and its fitting ?
Including said lockring - and suitable spacing.
The speedo drive is well greased - and intact - internally ?
If they become greaseless, their lifespan is limited after that ..
Out on the road, we were mystified when a thin black snake whipped across the road ahead of us. (!)
Until a Commando
ahead parked up, and examined his now seized speedo drive - spinning with the wheel -
and the cable ripped out of the speedo ...