And while we're on it, my MC28 motor has a clicking noise coming from the top cylinder when cold. Im sure it is powervalve related because, at idle and the pulley closes the PV you can hear the sharp rapid clicking and as the pulley opens the PV the noise goes away. If you hold your finger on the PV shaft, you can feel the vibrations of the clicking. It does not appear to come from the bottom cyl. The noise goes away as the motor warms up. Could someone please confirm my worst fear that the PV is contacting the piston/rings? Would have instead thought the noise would get louder/worse as everything got hotter/expanded and closer together. Any thoughts please?

Thanks very much
Richard