VESPA GTS Super 300 ie 2008, Service Station Manual

Page: 19 / 317

- 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.
- If the clearance is greater than that indicated in
the table, replace the piston.
N.B.
MEASURE THE CLEARANCE BY INSERTING THE BLADE
OF THE FEELER GAUGE FROM THE SECOND SEAL RING
SIDE.
Fitting clearance
Top piston ring - standard coupling clearance
0.015 - 0.06 mm
Top piston ring - maximum clear-
ance allowed after use
0.07 mm
Middle piston
ring - standard coupling clearance
0.015 - 0.06 mm
Middle piston ring - maximum clearance al-
lowed after use
0.07 mm
oil scraper ring - stand-
ard coupling clearance
0.015 - 0.06 mm
oil scraper
ring - maximum clearance allowed after use
0.07 mm
- Check that the head coupling surface is not worn
or misshapen.
- Pistons and cylinders are classified according to
their diameter. The coupling must be made with
those of the same type (M-M, N-N, O-O, P-P).
Characteristic
Maximum allowable run-out:
0.001 over 0.05 mm
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.
- If any measurements are greater than specified,
replace the piston rings.
N.B.
BEFORE REPLACING ONLY THE PISTON RINGS, ENSURE
THAT THE CLEARANCE BETWEEN THE PISTON RINGS
AND THE PISTON RING GROOVES, AND BETWEEN THE
PISTON AND THE CYLINDER, IS AS SPECIFIED. IN ANY
Vespa GTS Super 300 ie (2008)
Characteristics
CHAR - 19