Let me hop on board as well. Mini Z, 19 Kawasaki, starter assist kit upgrade 2 seasons ago. Starting was intermittent but nothing now. Same symptoms as the other posters- clicking solenoid.
I have interchanged existing relays (but have not bought new ones), cleaned and brushed all terminals and connections on solenoid, battery and ignition, installed new battery with 300/350 crank amps. I can jump the solenoid and it starts immediately. Suggestions?