PIAGGIO Runner 125 - Inspecting the Small End

Inspecting the small end
- Measure the internal diameter of the small end
using an internal micrometer.
N.B.
REPLACE THE CRANKSHAFT IF THE DIAMETER OF THE
ROD SMALL END EXCEEDS THE STANDARD DIAMETER
OR IT SHOWS SIGNS OF WEAR OR OVERHEATING.
Characteristic
Rod small end check-up: Maximum diameter
15.030 mm
Rod small end check-up: Standard diameter
15 +0.015+0.025 mm
Inspecting the wrist pin
- Measure the outer diameter of the gudgeon pin.
- Calculate the coupling clearance between pin
and connecting rod end.
- Measure the capacity diameter on the piston.
- Calculate the piston pin coupling clearance.
- Measure the outside diameter of the piston, per-
pendicular to the gudgeon pin axis.
- Carry out the measurement as shown in the fig-
ure.
125 cc: 41.1 mm (from crown)200 cc: 5 mm (from
bottom)
- 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 matching surface exhibits no
deformations or wear.
Maximum admissible displacement: 0.05 mm
- Pistons and cylinders are classified into catego-
ries based on their diameter. The coupling is car-
ried 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.
Engine Runner 125 - 200
ENG - 156