10 - 2
TRBL
SHTG
STARTING FAILURE/HARD STARTING/POOR IDLE SPEED
PERFORMANCE/POOR MEDIUM AND HIGH-SPEED PERFORMANCE
COMPRESSION SYSTEM
Cylinder and cylinder head
●
Loose spark plug
●
Loose cylinder head or cylinder
●
Broken cylinder head gasket
●
Broken cylinder gasket
●
Worn, damaged or seized cylinder
Piston and piston rings
●
Improperly installed piston ring
●
Worn, fatigued or broken piston ring
●
Seized piston ring
●
Seized or damaged piston
Valve, camshaft and crankshaft
●
Improperly sealed valve
●
Improperly contacted valve and valve seat
●
Improper valve timing
●
Broken valve spring
●
Seized camshaft
●
Seized crankshaft
POOR IDLE SPEED PERFORMANCE
POOR IDLE SPEED PERFORMANCE
Carburetor
●
Improperly returned starter plunger
●
Loose pilot jet
●
Clogged pilot jet
●
Clogged pilot air jet
●
Improperly adjusted idle speed
(Throttle stop screw)
●
Improper throttle cable play
●
Flooded carburetor
Electrical system
●
Faulty spark plug
●
Faulty CDI unit
●
Faulty pickup coil
●
Faulty charging/rotor rotation direction coil
●
Faulty ignition coil
Valve train
●
Improperly adjusted valve clearance
Air filter
●
Clogged air filter element
POOR MEDIUM AND HIGH-SPEED PERFORMANCE
POOR MEDIUM AND HIGH-SPEED PERFORMANCE
Refer to “STARTING FAILURE/HARD STARTING” and “POOR IDLE SPEED PERFORMANCE-
VALVE TRAIN”.
Carburetor
●
Improper jet needle clip position
●
Improperly adjusted fuel level
●
Clogged or loose main jet
●
Deteriorated or contaminated fuel
Air filter
●
Clogged air filter element
Summary of Contents for YFM660FS
Page 1: ...LIT 11616 17 14 5KM 28197 E2 YFM660FS SUPPLEMENTARY SERVICE MANUAL ...
Page 17: ...YAMAHA MOTOR CO LTD 2500 SHINGAI IWATA SHIZUOKA JAPAN PRINTED IN U S A ...
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Page 72: ...YFM660FP SERVICEMANUAL LIT 11616 15 01 5KM 28197 E0 ...
Page 117: ...2 11 SPEC MAINTENANCE SPECIFICATIONS Item Standard Cylinder head tightening sequence ...
Page 417: ...9 3 ELEC CHECKING THE SWITCH ...
Page 478: ...YAMAHA MOTOR CO LTD 2500 SHINGAI IWATA SHIZUOKA JAPAN PRINTED IN U S A ...