Yamaha YZF-R125 Service Manual: Removing the cylinder head

Yamaha YZF-R125 Service Manual / Engine / Cylinder head / Removing the cylinder head

1. Align:

  • "I" mark "a" on the generator rotor (with the stationary pointer "b" on the generator cover)

a. Turn the crankshaft counterclockwise.

b. When the piston is at TDC on the compression stroke, align the "I" mark "c" on the camshaft sprocket with the mark "d" on the cylinder head.

Removing the cylinder head


2. Loosen:

  • Camshaft sprocket bolt "1"

NOTE:

While holding the generator rotor nut with a wrench "2", loosen the camshaft sprocket bolt.

Removing the cylinder head


3. Remove:

  • Camshaft sprocket

NOTE:

To prevent the timing chain from falling into the crankcase, fasten it with a wire "1".

Removing the cylinder head


4. Remove:

  • Cylinder head

NOTE:

  • Loosen the bolts in the proper sequence as shown.
  • Loosen each bolt 1/2 of a turn at a time. After all of the bolts are fully loosened, remove bolts 1, 2, 4, and 6, and then remove the cylinder head with bolts 3 and 5 installed in the bolt holes.

Removing the cylinder head


    Cylinder head
    * Yamaha bond No. 1215 (Three Bond No. 1215) ...

    Checking the cylinder head
    1. Eliminate: Combustion chamber carbon deposits (with a rounded scraper) NOTE: Do not use a sharp instrument to avoid damaging or scratching: Spark plug bore threads Valve seats ...

    Other materials:

    Checking the clutch springs
    The following procedure applies to all of the clutch springs. 1. Check: Clutch spring Damage Replace the clutch springs as a set. 2. Measure: Clutch spring free length "a" Out of specification Replace the clutch springs as a set. ...

    Checking the bulbs and bulb sockets
    NOTE: Do not check any of the lights that use LEDs. Check each bulb and bulb socket for damage or wear, proper connections, and also for continuity between the terminals. Damage/wear  Repair or replace the bulb, bulb socket or both. Improperly connected Properly connect. No c ...

    Checking the cylinder and piston
    1. Check: Piston wall Cylinder wall Vertical scratches Replace the cylinder, and replace the piston and piston rings as a set. 2. Measure: Piston-to-cylinder clearance a. Measure cylinder bore "C" with the cylinder bore gauge. NOTE: Measure cylinder bore "C" by takin ...

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