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 ...

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    WARNINGBleed the hydraulic brake system whenever: the system is disassembled. a brake hose is loosened, disconnected or replaced. the brake fluid level is very low. brake operation is faulty. NOTE: Be careful not to spill any brake fluid or allow th ...

    Checking the rectifier/regulator
    1. Check: Rectifier/regulator output voltage Out of specification → Replace the rectifier/ regulator. a. Set the engine tachometer to the spark plug lead. b. Connect the pocket tester (DC 20 V) to the rectifier/regulator coupler as shown. Positive tester probe red "1" Negat ...

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