Yamaha YZF-R125 Service Manual: Incorrect engine idling speed

Yamaha YZF-R125 Service Manual / Troubleshooting / Incorrect engine idling speed

Engine

1. Cylinder and cylinder head

Incorrect valve clearance
Damaged valve train components

2. Air filter

Clogged air filter element

Fuel system

1. Throttle body

Damaged or loose throttle body joint
Improperly adjusted engine idling speed (idle adjusting screw)
Improper throttle cable free play
Flooded throttle body
Faulty air induction system

Electrical system

1. Battery

Discharged battery
Faulty battery

2. 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

3. Ignition coil

Broken or shorted primary or secondary coils
Faulty spark plug lead
Cracked or broken ignition coil

4. Ignition system

Faulty ECU
Faulty crankshaft position sensor
Broken generator rotor woodruff key

Starting failures

Engine 1. Cylinder and cylinder head - Loose spark plug - Loose cylinder head or cylinder - Damaged cylinder head gasket - Damaged cylinder gasket - Worn or damaged cylinder - Incorrect valve c ...

Poor medium-and-high-speed performance

Refer to "STARTING FAILURES" on page 9-1. Engine 1. Air filter Clogged air filter element Fuel system 1. Fuel pump Faulty fuel pump Faulty gear shifting Shifting is difficult Refer ...

Other materials:

Adjusting the front wheel static balance
NOTE: After replacing the tire, wheel or both, the front wheel static balance should be adjusted. Adjust the front wheel static balance with the brake discs installed. 1. Remove: Balancing weight(s) 2. Find: Front wheel's heavy spot NOTE: Place the front wheel on a suitab ...

Checking the crankshaft
1. Measure: Crankshaft runout Out of specification Replace the crankshaft, bearing or both. NOTE: Turn the crankshaft slowly. 2. Measure: Big end side clearance Out of specification Replace the crankshaft. 3. Measure: Crankshaft width Out of specification&nbs ...

Clutch lever
Clutch lever Clutch lever The clutch lever is located at the left handlebar grip. To disengage the clutch, pull the lever toward the handlebar grip. To engage the clutch, release the lever. The lever should be pulled rapidly and released slowly for smooth clutch operation. Th ...