Inspecting The Small End; Inspecting The Piston - VESPA GTV 250 i.e. 2008 Service Station Manual

Engine

Inspecting the small end

- Measure the internal diameter of the connecting
rod small end using an internal micrometer.
N.B.
REPLACE THE CRANKSHAFT IF THE DIAMETER OF THE
ROD SMALL END EXCEEDS THE STANDARD DIAMETER
OR IT SHOWS SIGNS OF WEAR OR OVERHEATING.
Characteristic
Connecting rod small end check-up: Maximum
diameter
15.030 mm
Connecting rod small end check-up: Standard
diameter
15+0.015+0.025 mm
Inspecting the wrist pin
- Measure the outer diameter of the gudgeon pin.
- Calculate the coupling clearance between pin
and connecting rod small end.
Characteristic
Pin diameter: Standard clearance
0.015 - 0.029 mm
Pin diameter Standard diameter
14.996 - 15.000 mm

Inspecting the piston

- Measure the diameter of the wrist pin seat on the
piston.
- Calculate the piston pin coupling clearance.
- Measure the outside diameter of the piston, per-
pendicular to the gudgeon pin axis.
- Take the measurement at 5 mm from the base in
the position shown in the figure.
- Carefully clean the seal housings.
- Measure the coupling clearance between the
sealing rings and the piston grooves using suitable
sensors, as shown in the diagram.
ENG - 122
Vespa GTV 250 i.e.