VESPA LX 4T USA Workshop Manual page 16

Characteristics
N.B.
MEASUREMENT "A" TO BE TAKEN IS A VALUE OF PISTON RE-ENTRY, IT INDICATES BY HOW
MUCH THE PLANE FORMED BY THE PISTON CROWN FALLS BELOW THE PLANE FORMED BY
THE TOP OF THE CYLINDER. THE FURTHER THE PISTON GETS INSIDE THE CYLINDER, THE
THINNER THE HEAD GASKET TO BE APPLIED SHOULD BE (TO RECOVER THE COMPRESSION
RATIO) AND VICE VERSA.
Characteristic
Shimming system to control the compression ratio
CR: 11.1 ÷ 12.9
Name
shimming_1
shimming_2
CHAR - 16
PISTON PROTRUSION CHECK
Measure A
0.05 ÷ 0.25
0.25 ÷ 0.40
LX 4T USA
Thickness
0.35
0.25