Removing The Piston - PIAGGIO 633823 Service Station Manual

Engine
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.
- If any measurements are greater than specified,
replace the piston rings.
N.B.
BEFORE REPLACING ONLY THE PISTON
RINGS, ENSURE THAT THE CLEARANCE BE-
TWEEN THE PISTON RINGS AND THE PISTON
RING GROOVES, AND BETWEEN THE PISTON
AND THE CYLINDER, IS AS SPECIFIED. IN ANY
CASE, NEW PISTON RINGS USED IN COMBI-
NATION WITH A USED CYLINDER MAY HAVE
DIFFERENT BEDDING CONDITIONS THAN
THE STANDARD.
Characteristic
Top piston ring
Standard opening: 0.15 ÷ 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 wrist pin stop ring onto the appropriate tool
- With opening in the position indicated on the tool
S = left
D= right
- Place the wrist pin stop ring into position using a
punch
- Fit the wrist pin stop using the plug as shown in
the figure
N.B.
ENG - 36
MP3 250 i.e.