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:

    Replacing the headlight bulbs
    The following procedure applies to the low beam headlight bulb. 1. Remove: Headlight bulb cover "1" 2. Remove: Headlight bulb holder "1" 3. Remove: Headlight bulb "1" WARNINGSince the headlight bulb gets extremely hot, keep flammable products and your ...

    Removing the rear brake master cylinder
    NOTE: Before removing the rear brake master cylinder, drain the brake fluid from the entire brake system. 1. Disconnect: Rear brake light switch coupler 2. Loosen: Rear brake light switch "1" 3. Remove: Rear brake master cylinder bolts Rear brake master cylinder 4. Remove: ...

    Types of bulbs
    The bulbs used on this vehicle are shown in the illustration. Bulbs "a" and "b" are used for the headlights and usually use a bulb holder that must be detached before removing the bulb. The majority of these types of bulbs can be removed from their respective socket by turning them coun ...

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