Yamaha YZF-R125 Service Manual: Poor medium-and-high-speed performance

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 loo ...

Shift pedal does not move

Shift shaft Improperly adjusted shift rod Bent shift shaft Shift drum and shift forks Foreign object in a shift drum groove Seized shift fork Bent shift fork guide bar Transmission ...

Other materials:

Troubleshooting method
The engine operation is not normal and the engine trouble warning light comes on. 1. Check: Fault code number a. Check the fault code number displayed on the FI diagnostic tool. b. Identify the faulty system with the fault code. Refer to "Self-Diagnostic Function table". c. Identi ...

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 ignition coil
1. Check: Primary coil resistance Out of specification  Replace. a. Disconnect the ignition coil connectors from the ignition coil terminals. b. Connect the pocket tester ( × 1) to the ignition coil as shown. Positive tester probe red/white "1" Negative tester probe orange ...