An odd noise on a stopped GS

[Orinoco]

I'd been out on a run on the GS (R1100GS 99), put back in the garage, then 3 hours later notice an odd sound coming from the bike, almost like water being poured out of a bottle or something electrical, but very quiet. It's coming from under the bike somewhere between the injector and under barrel on the right hand side.

I've disconnected the battery, but it's still there, weird... any ideas?

 

[Magnon]

Fuel tank venting excessive air pressure due to engine heat warming said tank which is probably low on fuel?

 

[Orinoco]

Refilled just 30 miles ago, so almost full; I'll open the fuel cap and see if it stops...

Nope, just did that, still happening almost 5 hours later...

 

[Deleted account 220427001]

ghost in the bike !"

 

[Slipperyeel]

Has it got a lead acid battery (as opposed to the sealed units ,which I think are gel?). Could that be venting?

 

[Streetbike]

It's just heaving a sigh of relief to be back safely.

 

[Orinoco]

It's just heaving a sigh of relief to be back safely.

 

[tonytobo]

is it oil running back to the sump?