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
    Although Yamaha motorcycles receive a thorough inspection before shipment from the factory, trouble may occur during operation. Any problem in the fuel, compression, or ignition systems, for example, can cause poor starting and loss of power. The following troubleshooting charts repre ...

    Adjusting the drive chain slack
    NOTE: The drive chain slack must be checked at the tightest point on the chain. CAUTION:A drive chain that is too tight will overload the engine and other vital parts, and one that is too loose can skip and damage the swingarm or cause an accident. Therefore, keep the drive ...

    Fi system
    The fuel pump delivers fuel to the fuel injector via the fuel filter. The pressure regulator maintains the fuel pressure that is applied to the fuel injector at only 250 kPa (2.50 kg/cm², 36.3 psi). Accordingly, when the energizing signal from the ECU energizes the fuel injector, the fuel ...

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