Checking The Piston - APRILIA RS4 125 Service Station Manual

RS4 125

Checking the piston

•
Measure the pin seat diameter on the
piston.
•
Calculate the pin - piston coupling
clearance.
•
Measure the piston outside diameter,
perpendicular to the pin axis.
•
Take the measurement at 6 mm (0.24
in) from the base, at the position shown
in the figure.
•
Carefully clean the sealing rings hous-
ings.
•
Measure the sealing rings - grooves
coupling clearance using suitable sen-
sors, as shown in the diagram
•
If clearances measured exceed the
limits specified in the table, the piston
should be replaced by a new one.
NOTE
MEASURE CLEARANCE BY INSERTING THE BLADE OF
THE FEELER GAUGE FROM THE 2nd SEALING RING
SIDE.
Characteristic
Piston / cylinder
Piston pin hole - standard: 15.003 - 15.008 mm
(0.5907 - 0.5908 in)
Maximum piston / cylinder coupling clearance
after use
- top ring: 0.075 mm (0.0029 in)
- middle ring: 0.065 mm (0.0025 in)
- oil scraper: 0.25 mm (0.0098 in)
Standard piston / cylinder coupling clearance
Engine
ENG - 187