DR Power RapidFire 5.5 HP Subaru (July 2013 - Present) Engine Manual - Manual (Page 18)

18 DR ® 5.8 HP ENGINE
6. ABNORMAL NOISES WHEN ENGINE IS RUNNING
TROUBLE CAUSE REMEDY
Beating sound
Piston, piston ring or cylinder is worn Replace the worn part
Connection rod or piston pin and piston pin hole are worn Replace the worn part
Crankshaft main neck is worn Replace bearing
Piston ring is broken Replace piston ring
Metal be
atin
g
sound
when
abnorm
al
combustion
o
ccurs
Too much carbon deposit in combustion chamber Clear away carbon deposit
Too small electrode clearance of spark plug Adjust electrode clearance properly
Too much fuel supplied to engine Check relative parts such as carburetor
Improper fuel brand Replace fuel
Engine is overheated Find the cause for overheating and eliminate it
Oth
er
problems
Improper valve clearance Readjust valve clearance properly
Flywheel is not connected with crankshaft tightly Connect tightly