Hi all just a quick question why does my speedo sometimes works then just drops off . If I come to a stop and go again it works as soon as I'm traveling at speed the needle drops bk down thanks mark

Remove the round white nylon drive from the gearbox sprocket nut and check that the slot for the cable drive is not rounded.
If so, replace but then check speedo gearbox is not stiff, oil if it is. Lever the dust seal over to allow oil in to the gear.

Failing that, look at the speedo inner cable for a break, the broken ends may grip for a while.