Compression System; Poor Idle Speed Performance; Poor Medium And High-Speed Performance - Yamaha YFM660FS Grizzly 4x4 Supplementary Service Manual

STARTING FAILURE/HARD STARTING/POOR IDLE SPEED
PERFORMANCE/POOR MEDIUM AND HIGH-SPEED PERFORMANCE

COMPRESSION SYSTEM

Cylinder and cylinder head
Loose spark plug
G
Loose cylinder head or cylinder
G
Broken cylinder head gasket
G
Broken cylinder gasket
G
Worn, damaged or seized cylinder
G
Piston and piston rings
Improperly installed piston ring
G
Worn, fatigued or broken piston ring
G
Seized piston ring
G
Seized or damaged piston
G

POOR IDLE SPEED PERFORMANCE

POOR IDLE SPEED PERFORMANCE
Carburetor
Improperly returned starter plunger
G
Loose pilot jet
G
Clogged pilot jet
G
Clogged pilot air jet
G
Improperly adjusted idle speed
G
(Throttle stop screw)
Improper throttle cable play
G
Flooded carburetor
G

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
G
Improperly adjusted fuel level
G
Clogged or loose main jet
G
Deteriorated or contaminated fuel
G
Valve, camshaft and crankshaft
Improperly sealed valve
G
Improperly contacted valve and valve seat
G
Improper valve timing
G
Broken valve spring
G
Seized camshaft
G
Seized crankshaft
G
Electrical system
Faulty spark plug
G
Faulty CDI unit
G
Faulty pickup coil
G
Faulty charging/rotor rotation direction coil
G
Faulty ignition coil
G
Valve train
Improperly adjusted valve clearance
G
Air filter
Clogged air filter element
G
Air filter
Clogged air filter element
G
10 - 2
TRBL
SHTG