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:

Starting the engine
In order for the ignition circuit cut-off system to enable starting, one of the following conditions must be met: The transmission is in the neutral position. The transmission is in gear with the clutch lever pulled and the sidestand up. 1. Turn the key to "ON" and make sure ...

Cleaning and lubricating the drive chain
The drive chain must be cleaned and lubricated at the intervals specified in the periodic maintenance and lubrication chart, otherwise it will quickly wear out, especially when riding in dusty or wet areas. Service the drive chain as follows. NOTICE The drive chain must be lubricated ...

Checking the connections
Check the leads, couplers, and connectors for stains, rust, moisture, etc. 1. Disconnect: Lead Coupler Connector 2. Check: Lead Coupler Connector Moisture → Dry with an air blower. Rust/stains → Connect and disconnect several times. 3. Check: All co ...