Incorrect Engine Idling Speed; Engine; Fuel System; Electrical Systems - Yamaha YJ50RN Service Manual

INCORRECT ENGINE IDLING SPEED/POOR MEDIUM-
AND-HIGH-SPEED PERFORMANCE/FAULTY CLUTCH
EAS00847

INCORRECT ENGINE IDLING SPEED

ENGINE

Air filter
• Clogged air filter element

FUEL SYSTEM

Carburetor
• Faulty starter plunger
• Loose or clogged pilot jet
• Loose or clogged pilot air jet
• Damaged or loose carburetor joint
• Improperly adjusted engine idling speed
(throttle stop screw)
• Improper throttle cable free play
• Flooded carburetor
Autochoke unit
• Faulty starter plunger
• Faulty ignitor unit
EAS00848

POOR MEDIUM-AND-HIGH-SPEED PERFORMANCE

Refer to "STARTING FAILURE/HEAD STARTING".
ENGINE
Air filter
• Clogged air filter element
EAS00853

FAULTY CLUTCH

ENGINE OPERATES BUT SCOOTER WILL NOT MOVE

V-belt
• Bent, damaged or worn V-belt
• Slipping V-belt
Primary pulley cam and primary pulley
slider
• Damaged or worn primary pulley cam
• Damaged or worn primary pulley slider
Transmission gear(s)
• Damaged transmission gear

CLUTCH SLIPS

Clutch shoe spring(s)
• Damaged, loose or worn clutch shoe
spring(s)
Clutch shoe(s)
• Damaged or worn clutch shoe(s)
Primary sliding sheave
• Seized primary sliding sheave

POOR STARTING PERFORMANCE

V-belt
• Slipping V-belt
• Oil or grease on the V-belt

ELECTRICAL SYSTEMS

Battery
• Discharged battery
• Faulty battery
Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap
Ignition coil
• Faulty spark plug lead
Ignition system
• Faulty ignitor unit
• Faulty pickup coil
FUEL SYSTEM
Carburetor
• Faulty diaphragm
• Incorrect fuel level
• Loose or clogged main jet
Primary sliding sheave
• Faulty operation
• Worn pin groove
• Worn pin
Clutch shoe(s)
• Bent, damaged or worn clutch shoe(s)
POOR ACCELERATION PERFORMANCE
V-belt
• Oil or grease on the V-belt
Primary pulley weight(s)
• Faulty operation
• Worn primary pulley weight(s)
Primary fixed sheave
• Worn primary fixed sheave
Primary sliding sheave
• Worn primary sliding sheave
Secondary fixed sheave
• Worn secondary fixed sheave
Secondary sliding sheave
• Worn secondary sliding sheave
8 - 2
TRBL
SHTG