Power steering help

Hi all

I've searched but cannot find anything that matches what my Zed has just gone and done.:cry: It has just dumped all of its power steering fluid when i parked up after a short drive,so i dropped it round to my local garage to see if it was a high pressure hose or a clip that had come off. Having checked it they are at a loss as when the engine is running there are no leaks or loss of fluid or power assistance, however, as soon as the engine is switched off the fluid spews out the top of the reservoir and from the seal around the pulley shaft.:eek: Have you ever heard of this before or any idea so i can point my guy in the right direction, its almost as if a pressure relief valve is stuck somewhere.Here's hoping someone can help quickly as it's far too cold to be going to work on the motorbike:(

Sean