Inspecting The Small End; Inspecting The Wrist Pin; Inspecting The Piston - PIAGGIO MSS ZIP 100 4T Service Manual

Engine

Inspecting the small end

- Measure the internal diameter of the small end
using an internal micrometer.
N.B.
IF THE DIAMETER OF THE ROD SMALL END EXCEEDS
THE MAXIMUM DIAMETER ALLOWED, SHOWS SIGNS OF
WEAR OR OVERHEATING REPLACE THE CRANKSHAFT
AS DESCRIBED IN THE "CRANKCASE AND CRANK-
SHAFT" CHAPTER".
Characteristic
Max. diameter admitted: check the small end
13.030 mm
Standard diameter: check the small end
13 +0.025+0.015mm

Inspecting the wrist pin

- Measure the outer diameter of the gudgeon pin.
Characteristic
Standard diameter: gudgeon pin
13 -0-0.004mm
Minimum admissible diameter gudgeon pin
12.990 mm

Inspecting the piston

- Carefully clean the sealing rings housings with the aid of an old piston ring.
- Measure the coupling clearance between the sealing rings and the piston grooves using a thickness
gauge, as shown in the figure.
- If the clearances detected exceed the limits specified in the table, the piston and the piston rings should
be replaced.
Name
Top piston ring
Middle piston ring
oil scraper
ENG - 90
PISTON
Description Dimensions
0.030 ÷ 0.065 mm
0.020 ÷ 0.055 mm
0.040 ÷ 0.160 mm
MSS ZIP 100 4T
Initials Quantity
0.080 mm
0.070 mm
0.20 mm