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:

    Checking the drive chain
    1. Measure: 15-link section "a" of the drive chain Out of specification Replace the drive chain. a. Measure the length "a" between the inner sides of the pins and the length "b" between the outer sides of the pins on a 15-link section of the drive chain as shown in the illustration. ...

    Removing the front fork legs
    The following procedure applies to both of the front fork legs. 1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Loosen: Handlebar pinch bolt "1" Handlebar bolt "2" Upper bracket ...

    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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