Derbi GPR 125 Racing, Workshop Manual

Page: 141 / 247

4 - ENGINE
141
CALCULATING THE BOTTOM GASKET THICKNESS
THE CYLINDER GASKET THIC-
KNESS MUST BE CALCULATED
TO ESTABLISH THE APPROPRIATE
COMPRESSION RATIO.
PERFORM THE CALCULATION
WITH THE COMPARATOR GAUGE
WITHOUT FITTING ANY CYLIN-
DER BOTTOM GASKET.
1. Fit:
- The comparer (1) onto the TDC measuring tool (2).
PLACE THE COMPARER ON A
FLAT SURFACE AND ADJUST
CORRECTLY (0).
2. Fije:
- The TDS measuring tool (2), by means of two M8 bots
for securing the cylinder head to the crankcase (3).
TDC measuring tool:
Ref.
864592
3. Position:
- The piston at TDC.
- Take a reading of the measurement on the comparer.
4. Choose:
- The cylinder base gasket (see table).
THERE ARE THREE THICKNESSES
OF GASKET AVAILABLE:
0.3, 0.4 AND 0.5 MM.
TDC measurement (mm)
0.95 / 1.09
1.1 / 1.25
1.26 /1.45
Thickness of Gasket (mm)
0.3 ± 0.05
0.4 ± 0.05
0.5 ± 0.05
Reference
CM157501
CM157502
CM157503
1
2
3
3
2
N.B.
N.B.
N.B.