Old memories...! 4 Hex bolts on the bottom of the back cover, a little fiddly to get at if the plastic is on, but stick a mirror in there first then you should be able to see them.
But my early K did have condensation problems inside the cluster, plenty of it because I had to park it or ride it in cold rainy weather quite often. I fixed that by venting it, a few very small
holes on the back of the instruments top and bottom did the trick. Then I took it to the shop for some other work, heated grips ????, they took the cluster off to do that, noticed the holes and plugged them with sillycone.....the buggers!!! Next day or so, cluster still full of condensation.....Grrrr! Had to go back in there and remove the sillycone.
Later went back to my mechanic and explained it to him and.......he started doing that same mod to other bikes.
But since you are going in there you can do what I did also, that is lube the electronics/contacts/gears with some high quality dielectric lube, the marine stuff is always good, may save you from a dead speedo and unwarranted performance awards....!