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:

    Troubleshooting
    The ignition system fails to operate (no spark or intermittent spark). NOTE: Before troubleshooting, remove the following part(s): 1. Seats 2. Fuel tank 3. Right side cover 4. Left side panel 5. Left upper side cowling ...

    Installing the exhaust assembly
    1. Install: Exhaust assembly "1" Exhaust pipe nuts "2" Exhaust assembly bolts "3" "4" NOTE: Do not fully tighten the nuts and bolts. 2. Tighten: Exhaust pipe nuts "2" Exhaust assembly bolt "4" Exhaust assembly bolt "3" ...

    Checking the fuel line
    1. Remove: Left side panel Refer to "GENERAL CHASSIS" on page 4-1. 2. Lift the fuel tank. (Do not disconnect the fuel hose, drain hose 3. Check: Fuel hose "1" Cracks/damage → Replace. Loose connection Connect properly. 4. Install: Fuel tank Refer to "FUEL TANK" on pa ...

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