Hi, anyone experienced this before? just started up for first time this year and the rev counter is playing up, it,s reading 5 or 6K on tickover and just a moderate blip of the throttle sees it going full scale into the red? Sender issue or clock? Thanks.

Would start by re-seating connectors at rev counter and ignition control box.

dont forget to check your battery with a multimeter, if its over-charging it can cause some kinda crappy symptoms like this

the other more commeon one as magg said is a bad connectionsomewhere, this could be a corroded earth from sitting with moisture or the connectors themselves.