Thanks for the responses, I've fitted a new diaphragm and cover plate but am still getting a drip, next thing is to remove from handlebars and try to trace the leak. I've also checked both callipers and replaced the pads as the originals seemed to be oily and there was a deposit of some sort on the discs. All cleaned and reassembled but the brake is still suicidal! Maybe I need to bed the pads in a little? Or maybe I'm expecting too much? My other bike is a BMW R Nine T with Brembos and will stop on a sixpence!