Yamaha YZF-R125 Service Manual: 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 from the piston ring grooves and piston rings.


Checking the piston rings


2. Install:

  • Piston ring (into the cylinder)

NOTE:

Level the piston ring into the cylinder with the piston crown.

Checking the piston rings


a. 40 mm (1.57 in)

3. Measure:

  • Piston ring end gap Out of specification Replace
    the piston ring.

NOTE:

The oil ring expander spacer end gap cannot be measured. If the oil ring rail gap is excessive, replace all three piston rings.


    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. Mea ...

    Checking the piston pin
    1. Check: Piston pin Blue discoloration/grooves  Replace the piston pin and then check the lubrication system. 2. Measure: Piston pin outside diameter "a" Out of specification ...

    Other materials:

    Checking the steering head
    1. Wash: Bearings Bearing races 2. Check: Bearings Bearing races Damage/pitting →Replace. 3. Replace: Bearings Bearing races a. Remove the bearing races from the steering head pipe with a long rod "1" and hammer. b. Remove the bearing race from the lower bracket ...

    Checking the valves and valve guides
    The following procedure applies to all of the valves and valve guides. 1. Measure: Valve-stem-to-valve-guide clearance Out of specification Replace the valve guide. Valve-stem-to-valve-guide clearance = Valve guide inside diameter "a" - Valve stem diameter "b" 2. Replace: ...

    Checking the brake fluid level
    Front brake Front brake Minimum level mark Rear brake Rear brake Minimum level mark Insufficient brake fluid may allow air to enter the brake system, possibly causing it to become ineffective. Before riding, check that the brake fluid is above the minimum level mark an ...

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