Hissing sound from near shock?

Took bike out today and when got back there was a hissing noise from rear shock area, at first I thought I had a puncher but none found and the sound was definitely coming from around the shock area, but after 5 mins or so it stopped, I started the bike again run for a while and turned it off but no hissing. All I can put it down to is maybe a breather pipe/valve or something but ive not noticed it before. Has anyone else had the same happen or know what it could be ?

There is a fuel tank breather located right by the top shock mount! My bet is thats it! Next time you hear it just open your petrol cap and i bet it stops!

Fingers crossed for a build up of pressure in the tank and that was it. If it was from the shock then all that lovely gas would now be gone and it wouldn't perform at all. I'm sure it was the tank though.

Was that you on a ride out today with a KTM 950 Supermoto and a red R1? On Reevesby Bends into Horncastle?

Might be a loose spark plug?

My SD also had hissing sound from the area near rear shock and rear wheel. The exhaust heats up the air inside swingarm and the air then comes out from small holes. So my swingarm was leaking from the hole where the brake line fitting is connected to the swingarm If you twist the fitting then you can release the pressure from the swingarm.