PIAGGIO Beverly Tourer 125, Service Station Manual

Page: 118 / 278

Top piston ring - standard coupling clearance
0.025 ÷ 0.07 mm
Top piston ring - maximum clear-
ance allowed after use
0.08 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
Inspecting the cylinder
- Using a bore meter, measure the inner cylinder
diameter at three different points according to the
directions shown in the figure.
- Check that the head coupling surface is not worn
or misshapen.
- Pistons and cylinders are classified according to
diameter. The coupling is carried out in pairs (A-A,
B-B, C-C, D-D).
- The cylinder rectifying operation should be car-
ried out with a surfacing that respects the original
angle.
- The cylinder surface roughness should be 0.9
micron.
- This is indispensable for a good seating of the
sealing rings, which in turn minimises oil consump-
tion and guarantees optimum performance.
- The pistons are oversized due to cylinder grind-
ing and are subdivided into three categories- 1st,
2nd, 3rd corresponding to 0.2-0.4-0.6 mm oversi-
Engine
Beverly 125
ENG - 118