2004-2006 Kawasaki 900 STX Jet Ski Service Manual, Page 236Get this manual
APPENDIX 16-5 Troubleshooting
Low engine power (This trouble often has more than one cause, and trouble symptoms may not be clear) Ignition System
Spark plug gap or heat range wrong Ignition timing wrong Reduced ignition coil output Loose wiring connection in ignition circuit
Fuel System
Insufficient fuel supply to carburetor Carburetor diaphragm damaged Pulse line leaking or clogged Throttle valve does not fully open Fuel filter screen clogged Faulty fuel pump