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

Yamaha YZF-R125 Service Manual / Troubleshooting / 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 to "Clutch drags".

    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:

    Checking the front fork
    1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Check: Inner tube Damage/scratches Replace. Oil seal Oil leakage Replace. 3. Hold the vehicle upright and apply the front brake. 4. Che ...

    Fi system
    The fuel pump delivers fuel to the fuel injector via the fuel filter. The pressure regulator maintains the fuel pressure that is applied to the fuel injector at only 250 kPa (2.50 kg/cm², 36.3 psi). Accordingly, when the energizing signal from the ECU energizes the fuel injector, the fuel ...

    Installing the crankshaft
    1. Install: Crankshaft "1" NOTE: Install the crankshaft with the crankshaft installer pot "2", crankshaft installer bolt "3", adapter (M12) "4" and spacer (crankshaft installer) "5". CAUTION:To avoid scratching the crankshaft and to ease the installation procedure, lubricate ...

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