2008 Kawasaki JET SKI STX-15F Owners Manual - Page 129

MAINTENANCE AND ADJUSTMENTS 127 Valve Clearance Valve and valve seats wear decreasing valve clearances, and upsetting valve timing. Spark Plug The standard spark plug is NGK CR9EK set to a 0.7 a 0.8 mm (0.028 a 0.032 inch) gap. Since the engine is water-cooled and is generally operated at a constant throttle opening, cylinder head temperature is relatively stable. For this reason, if the engine is in good condition and properly tuned, it should not be necessary to use a spark plug of a different heat range. Since a spark plug of the wrong heat range can cause extensive engine damage, only the standard spark plug is recommended. CAUTION If valve clearance is left unadjusted, wear will eventually cause the valves to remain partially open, which lowers performance, burns the valves and valve seats, and may cause serious engine damage. Valve clearance for each valve should be checked and adjusted in accordance with the Periodic Maintenance Chart. Inspection and adjustment should be done by an authorized Kawasaki dealer. INTAKE 0.15 a 0.24 mm (0.0059 a 0.0094 in.) EXHAUST 0.22 a 0.31 mm (0.0087 a 0.0122 in.) j