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:

    Removing the handlebars
    1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Remove: Handlebar grip "1" NOTE: Blow compressed air between the handlebar and the handlebar grip, and gradually push the grip off the handleb ...

    Checking the starter clutch
    1. Check: Starter clutch rollers "1" Starter clutch spring caps "2" Starter clutch springs "3" Damage/wear Replace the starter clutch assembly. 2. Check: Starter clutch idle gear Starter clutch gear Burrs/chips/roughness/wear Replace the defective part(s). 3. Check: ...

    Checking the valve springs
    The following procedure applies to all of the valve springs. 1. Measure: Valve spring free length "a" Out of specification Replace the valve spring. 2. Measure: Compressed valve spring force "a" Out of specification Replace the valve spring. b. Installed length 3. ...

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