Inspecting The Piston - Derbi Rambla 250 Manual

Engine
Inspecting the wrist pin
- Check the pin outside diameter
- Calculate the rod small end - gudgeon pin cou-
pling clearance.
Characteristic
Pin diameter: Standard clearance
0.015 ÷ 0.029 mm
Pin diameter: Standard diameter
14.996 ÷ 15.000 mm

Inspecting the piston

- Measure the pin seat diameter on the piston.
- Calculate the pin - piston coupling clearance.
- Measure the piston outside diameter, perpendic-
ular to the pin axis.
- Take the measurement at 5 mm from the base,
at the position shown in the figure.
- Carefully clean the sealing rings housings.
- Measure the sealing rings - grooves coupling
clearance using suitable sensors, as shown in the
diagram
- If clearances measured exceed the limits speci-
fied in the table below, the piston should be re-
placed by a new one.
NOTE
MEASURE CLEARANCE BY INSERTING THE BLADE OF
THE THICKNESS GAUGE FROM THE 2nd SEALING RING
SIDE.
NOTE
THE PIN HOUSINGS HAVE TWO LUBRICATION CHAN-
NELS FOR THIS REASON MEASURE THE DIAMETER AC-
CORDING TO THE PISTON AXIS.
Characteristic
Pin seat diameter on piston : Standard diame-
ter
15.001 ÷ 15.006 mm
Pin seat diameter on piston : Standard clear-
ance
0.001 ÷ 0.010 mm
ENG - 111