Derbi GP1 125-250 c.c. Workshop Manual page 110

- Take the measurement 5 mm from the base in the position
shown in the figure.
- Carefully clean the sealing ring housings.
- Using suitable probes, measure the coupling clearance
between sealing rings and piston housings, as shown in the
figure.
- If higher clearance values than those reported in the table
are measured, replace the piston.
N.B.
MEASURE THE CLEARANCE BY INSERTING THE BLADE OF THE
THICKNESS GAUGE FROM THE SIDE OF THE SECOND GAS
RING
N.B.
THE HOUSINGS OF THE PIN HAVE TWO LUBRICATION CHAN-
NELS. FOR THIS REASON MEASUREMENT OF THE DIAMETER
MUST BE CARRIED OUT ACCORDING TO THE AXIS OF THE
PISTON.
Characteristic
Diameter of pin seat on piston : Standard diameter
15,001 ÷ 15,006 mm
Diameter of pin seat on piston : Standard clearance
0,001 ÷ 0,010 mm
Piston diameter
71,953 ÷ 71,981 mm
FITTING CLEARANCE
1st lining - Standard coupling clearance
0,015 ÷ 0,06 mm
1st lining -Admissible clearance after use
0,07 mm
2nd lining - Standard coupling clearance
0,015 ÷ 0,06 mm
2nd lining - Admissible clearance after use
0,07 mm Scraper ring
Standard coupling clearance
0,015 ÷ 0,06 mm Scraper ring
Admissible clearance after use
0,07 mm
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