how about clean and relube the speedo cable - it might be worth a shot! plus it might even solve the sticky speedo. worked for me once as i too had a jumpy speedo and found it very annoying.
I think almost all Royal Enfields have a "cush drive" between the rear sprocket and the actual wheel.One of the advantages of these was it cushioned the shock of changing gears etc.Another feature that went along with these was you should be able to remove the rear wheel without loosening or changing the rear sprockets location.At least on the Bullets, removing the axle and spacer (without loosening the sprocket nut or rear brake backing plate stud) allows the rear wheel to move sideways, disengaging the cush drive and allowing it to just slide out for tire repair.
I put about three hundred miles on my bike today (round trip,) and noticed some odd things:After about an hour ........ snip