Doosan DX60R Shop Manual page 266

Every 1000 Hours of Operation
Perform the following maintenance every 1000 hours of
operation.
• Adjust Intake / Exhaust Valve Clearance
Adjust Intake / Exhaust Valve Clearance
Proper adjustment is necessary to maintain the correct timing
for opening and closing the valves. Improper adjustment will
cause the engine to run noisily, resulting in poor engine
performance and engine damage. See "Intake / Exhaust Valve
and Guide" on page -95
Engine SP001693
Page 86