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:

    Identification
    Vehicle identification number The vehicle identification number "1" is stamped into the right side of the steering head pipe. Model label The model label "1" is affixed to the frame. This information will be needed to order spare parts. ...

    Checking the swingarm
    1. Check: Swingarm Bends/cracks/damage   Replace. 2. Check: Pivot shaft Roll the pivot shaft on a flat surface. Bends Replace. WARNINGDo not attempt to straighten a bent pivot shaft. 3. Wash: Pivot shaft Washer Swingarm adjusting collar Du ...

    Air induction system
    1. Air induction system hose (air filter case to reed valve assembly) 2. Air induction system reed valve assembly 3. Air induction system hose (reed valve assembly to exhaust pipe) Checking the air induction system Air injection The air induction system burns unburned exhaust gases b ...

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