Hello everyone, I'm new to the board and just picked up a 1990 k100, really pleased especially now I've finally found how to get the panniers off.............
The front brakes are a bit noisy but I'm changing the pads and feel sure that will cure it.
The only thing that's puzzling me is there is a very slight hissing noise from the left as your sitting on the bike, sort of under the radio. It's not loud and sounds almost like it should be there but I thought I would ask the question.
It;s particularly noticeable because I ride with my dog and no helmet just up the lane and back so I can hear it.

Any clues would be appreciated................

My guess is it's the fuel pump singing away as they do. Is it only when the motor's running?

Yep only when the engines running Ned,
It sounds like your letting a tyre down very very slowly
ish

If you undo the petrol cap then run it you should hear it a bit more, as said its proberbly the petrol pump.

Pads noisey.... if they squeal a smear of high melting point to the back of the pads should cure it.
Is the hissing due to pressure in the tank? When you open it does it pop? If so it may be you have pinched the pressure relief tube from beneath the tank.
Ajays.

Pads are pretty low so changing them front and back when they arrive. More of a horrible grinding than squealing
opened the tank as suggested by badgerdid and it's the fuel pump just sounds to be going along nicely.
New bike paranoia