The odometer and trip meter n my K100 RT dont work. I have a couple of spares. One consists of most of the internal workings including a complete speedo with what look like good gears etc. I can see that it is connected to the rest of the panel wiring by 3 grey wires. What I want to do, I think, is test that the speedo actually works before I swap it over. So the question is how. I assume I can either test the resistances between the grey wires or apply a voltage across them to test. Mainly I want to see if the speedo moves as it should as I can work the odometer and trip meter by hand and everything there seems good. Can anybody help?

Remove the speed sensor (don't disconnect it) and hold a 240v soldering iron right next to the sensor. The magnetic field will induce a signal so the speedo registers 61kph as long as the key is on. Plug the other speedo in and test it.
On the big plug there are 2 types of pins round and square from what I gather they don't mix well.

Thanks Rick. Sounds easy enough. Will this also make the odometer gears move as well?

It sure will.