Removing The Piston - VESPA GTV 250 i.e. 2008 Service Station Manual

Engine
Inspecting the piston rings
Sealing rings
- Alternately insert the three sealing rings into the
cylinder, in the area where it retains its original di-
ameter. Using the piston, insert the rings perpen-
dicularly to the cylinder axis.
- Measure the opening (see figure) of the sealing
rings using a feeler gauge.
- Replace the piston rings if values higher than
those prescribed are measured.
N.B.
BEFORE REPLACING ONLY THE PISTON RINGS, MAKE
SURE THAT COUPLING CLEARANCE BETWEEN THE
SEAL RINGS AND ITS GROOVES, AND THAT BETWEEN
THE PISTON AND THE CYLINDER ARE AS SPECIFIED. IN
ANY CASE, NEW PISTON SEALING RINGS USED IN COM-
BINATION WITH A USED CYLINDER MAY HAVE DIFFER-
ENT BEDDING CONDITIONS THAN THE STANDARD
ONES.
Characteristic
Top piston ring
Standard opening: 0.15 to 0.30 mm
Middle piston ring
Standard opening: 0.20 - 0.40 mm
scraper ring
Standard opening: 0.20 - 0.40 mm

Removing the piston

- Install piston and wrist pin onto the connecting
rod, aligning the piston arrow the arrow facing to-
wards the exhaust.
- Fit the pin retainer ring onto the appropriate tool
- With opening in the position indicated on the tool
S = left
D= right
- Place the wrist pin retainer ring into position using
a punch
- Fit the pin retainer ring using the plug as shown
in the figure
N.B.
ENG - 124
Vespa GTV 250 i.e.