Digital Speedometer keeps resetting

mount the speedo and speedo wires on the far left of handle bars and keep the killswitch wires to the far right of handle bars,and this will work most of the time.
if you still have problems mount the speedo on a mount 4 or 5 inches in front of the handle bars on left side,the goal is to put the speedo far as u can from the cdi and killswitch wires.

I would change your plug wire to a good quality emi suppression type. That fixed my problem.