Fuel tap -101 OCTANE- vacuum - Yamaha BW's Spy, Bump, N.G., Suzuki Katana AY - three connections

Vacuum controlled fuel cock for Yamaha and Suzuki scooters.
Often a malfunction of this component leads to starting difficulties and engine misfires while driving.
The fuel cock diaphragm hangs and releases the fuel not or only in insufficient measure.
The only solution is a complete replacement.