Yamaha YZF-R125 Service Manual: Checking the cylinder head

Yamaha YZF-R125 Service Manual / Engine / Cylinder head / 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

Checking the cylinder head


2. Check:

  • Cylinder head Damage/scratches   Replace.

  • Cylinder head water jacket Mineral deposits/rust
    Eliminate.

3. Measure:

  • Cylinder head warpage Out of specification Resurface
    the cylinder head.

a. Place a straightedge "1" and a thickness gauge "2" across the cylinder head.

Checking the cylinder head


b. Measure the warpage.

c. If the limit is exceeded, resurface the cylinder head as follows.

d. Place a 400-600 grit wet sandpaper on the surface plate and resurface the cylinder head using a figure-eight sanding pattern.

NOTE:

To ensure an even surface, rotate the cylinder head several times.

    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 compre ...

    Checking the camshaft sprocket and timing chain guide
    1. Check: Camshaft sprocket More than 1/4 tooth wear "a" Replace the camshaft sprocket, timing chain and crankshaft as a set. a. 1/4 tooth b. Correct 1. Timing chain roller 2. C ...

    Other materials:

    Important manual information
    Particularly important information is distinguished in this manual by the following notations: This is the safety alert symbol. It is used to alert you to potential personal injury hazards. Obey all safety messages that follow this symbol to avoid possible injury or death. WARNING ...

    Removing the rear brake caliper
    NOTE: Before disassembling the brake caliper, drain the brake fluid from the entire brake system. 1. Remove: Union bolt "1" Copper washers "2" Brake hose "3" NOTE: Put the end of the brake hose into a container and pump out the brake fluid carefully. ...

    Replacing the air filter element and cleaning the check hose
    The air filter element should be replaced at the intervals specified in the periodic maintenance and lubrication chart. Have a Yamaha dealer replace the air filter element more frequently if you are riding in unusually wet or dusty areas. In addition, the air filter check hose must be ...

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