Yanmar 4LHA-HTP Operation Manual page 56

2 Lapping of Intake/Exhaust Valves
Adjustment necessary to maintain proper contact of valves and seats.
This maintenance requires specialized knowledge.
Consult your Yanmar dealer or distributor.
(3) Inspection and Adjustment of Fuel Injection Timing
Fuel injection timing must be adjusted to ensure optimal engine performance.
This maintenance requires specialized knowledge.
Consult your Yanmar dealer or distributor.
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