Inspecting The Piston; Removing The Piston - Derbi boulevard 125 4t Workshop Manual

Engine
- The pistons are oversized due to cylinder rectifi-
cation and are subdivided into three categories
1st, 2nd, 3rd with 0.2-0.4-0.6 mm oversize. They
are also classified into 4 categories A-A, B-B, C-
C, D-D.

Inspecting the piston

- Carefully clean the seal housings.
- Measure the coupling clearance between the seal rings and the grooves using suitable sensors, as
shown in the diagram.
- If the clearance is greater than that indicated in the table, replace the piston.
Name
Top piston ring
Middle piston ring
oil scraper
Name
Top piston ring
Middle piston ring
oil scraper

Removing the piston

- Install piston and wrist pin onto the connecting
rod, aligning the piston arrow the arrow facing to-
wards the exhaust.
- Fit the pin stop ring onto the appropriate tool.
Specific tooling
020430Y Pin lock fitting tool
STANDARD COUPLING CLEARANCE
Description Dimensions
0.025 ÷ 0.070
0.015 ÷ 0.060
0.015 ÷ 0.060
MAXIMUM ADMITTED CLEARANCE AFTER USE
Description Dimensions
Initials
Initials
0.080 mm
0.070 mm
0.070 mm
Quantity
Quantity
ENG - 111