Yamaha YZF-R125 Service Manual: Checking the cylinder and piston

Yamaha YZF-R125 Service Manual / Engine / Cylinder and piston / 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.

Checking the cylinder and piston


NOTE:

Measure cylinder bore "C" by taking side-to-side and front-to-back measurements of the cylinder.

Then, find the average of the measurements.


b. If out of specification, replace the cylinder, and replace the piston and piston rings as a set.

c. Measure piston skirt diameter D "a" with the micrometer.

Checking the cylinder and piston


b. 5.0 mm (0.20 in) from the bottom edge of the piston


d. If out of specification, replace the piston and piston rings as a set.

e. Calculate the piston-to-cylinder clearance with the following formula.


f. If out of specification, replace the cylinder, and replace the piston and piston rings as a set.

    Removing the piston
    1. Remove: Piston pin clips "1" Piston pin "2" Piston "3" CAUTION:Do not use a hammer to drive the piston pin out. NOTE: Before removing the piston pin c ...

    Checking the piston rings
    1. Measure: Piston ring side clearance Out of specification Replace the piston and piston rings as a set. NOTE: Before measuring the piston ring side clearance, eliminate any carbon deposits ...

    Other materials:

    Installing the rear wheel (disc)
    1. Install: Rear brake disc NOTE: Tighten the brake disc bolts in stages and in a crisscross pattern. 2. Check: Rear brake disc Refer to "CHECKING THE REAR BRAKE DISC" on page 4-33. 3. Lubricate: Rear wheel axle Contact surface of rear wheel hub and rear wheel Whee ...

    Troubleshooting
    Any of the following fail to light: headlight, high beam indicator light, taillight, license plate light, auxiliary light or meter light. NOTE: Before troubleshooting, remove the following part(s): 1. Seats 2. Fuel tank ...

    Assembling the water pump
    1. Install: Water pump seal "1" (into the water pump housing "2") CAUTION:Never lubricate the water pump seal surface with oil or grease. NOTE: Install the water pump seal with the special tools. Install the water pump seal with the special tools to the specifi ...

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