Never ever put such a hot plug in your aircooled two stroke - the engine will knock, lose power and damage its connecting rod at high rpms.
The correct heat range for the Kawasaki KH series engines is NGK heat range 8 - the OEM plug is B8ES - regular firing nose, extended nose cold plug - adjust your carb to fatory specs and see how controlled the power is after installing this plug.
The correct plug for the RX, RS and YB engines is half length, projected nose cool range plug. Only mess about with heat range if you know what you are doing. The reason is that the compression ratio is quite high on these engines which causes pre-ignition if you run a hot plug.