Hi, I have a 1985 K100RS, and noticed that under the fuel tank there are 3 plugs/ sockets that do not connect to anything. They obviously do not plug into each other.

Image here, I have circled the plugs/ sockets in question  https://ibb.co/9hDzXMW

I believe the bike ran OK until it developed a fuel pump voltage supply issue.

Maybe these are for different variants of the K100 ? Or am I missing something ?

Since it ran without the plugs connected, it's not a problem. The bottom one for example is the connection for additional instruments (eg. fuel level gauge) Can't see the colours for the others,  but you will find it on the wiring diagrams available on this forum at portal/k100 forum tech page/electrical/electrical diagrams.

The socket for the heated grips is under the tank.

Top most connector- Two pin round terminals (brown, green, black) = heated grips

Three pin flat terminals (brown, green, ?) = hazard switch
Three pin round terminals (brown, blue, green/black)= connector for additional instruments Temp gauge or fuel gauge

Careful with the fuel level sender= fuel pump power
No longer available

Thanks for the replies, puts my mind at ease. I checked the bike again and sure enough the hazards and grip heaters do not work. Other electrics seem OK. Will move on to the underlying problem.

Just out of curiosity how did you end up with a K Bike in Moresby?  How far can you go, for instance Rogers/Lae Lae, Sogeri or Rigo?  

My first bike was a Suzuki TC100 which I learnt to ride around there as I lived in Korobosea then Hohola.

Most bikes here are brought in from Australia and stay here. Guys import themselves, this K was previously owned by an Australian who has since gone finish, also had a K75 will post a picture of the other BMWs soon.
I'm in Port Moresby, we have a club that goes out on a Sunday. Favorite ride is Sogeri, also Kwikila, off Maggi Highway. Sometimes Lealea. Hiritano highway is pretty impassible nowadays without a dirt bike, will not take my F800GS. That used to be a good run