Its working intermittently at the moment, Tends to come back on occasionally if i get the revs fairly high or lean quite far over on right bends (if i lean quite a lot over on the left asnd its working it will stop) thought it might be catching somewhere and lose (wiggling it has worked occasionally) but im useless at this kind of thing, any ideas? It is really interfering with my plan to get him to a million miles....

Check and clean the 2-prong connector under the right battery cover, for the cable that goes from the speedo sensor in the final drive into the harness.

  Also, remove and check the multipin connectors on the back of the speedometer.  It's going to take major fairing surgery to get at them but it's worth the effort.  https://www.k100-forum.com/t2386-getting-to-the-speedometer-on-a-k100-rt

If you feel so inclined, there are problematic connectors inside the speedo that can be examined and cleaned; however it means opening the speedo case to get at them.  Don't know how brave you feel.  
https://www.k100-forum.com/t3209-speedo-help