Inspecting The Cylinder - Derbi GP1 125-250 c.c. Workshop Manual

I I
NSPECTING THE CYLINDER NSPECTING THE CYLINDER
Version 250
- Using a bore gauge, measure the internal diameter of the
cylinder following the directions given in the figure and at
three different heights.
- Check that the plane of coupling with the head does not
show wear or deformations.
- The pistons and cylinders are classified with categories de-
pending on the diameters. The coupling is carried out mat-
ched (A-A, B-B, C-C, D-D).
Characteristic
cylinder: standard diameter
71,990 ÷ 72,018 mm (a 33 mm)
Maximum allowable runout:
0,05 mm
Version 125
- Using a bore measuring device, measure the cylinder bore
in the directions shown in the figure and at three different
heights.
- Ensure there are no signs of wear or deformation on the
surface of the cylinder that mates with the cylinder head.
- Pistons and cylinders are categorised according to their
diameter. Pistons should match with cylinders of the same
classification (A-A, B-B, C-C, and D-D).
- Cylinder re-bores must be carried out respecting the origi-
nal matching angle on the bored surface of the cylinder.
- The surface roughness of the bored surface of the cylinder
should be 0.9 micron.
- This is necessary in order to ensure the proper bedding-in
of the piston rings, thus reducing oil consumption and provi-
ding optimum performance.
- 1st, 2nd and 3rd over-sized pistons are available as spare
parts, for re-bored cylinders, corresponding to 0.2, 0.4 and
0.6 mm over-sizes, respectively. There are four categories for
matching oversize cylinders (A-A, B-B, C-C, and D-D).
Characteristic
cylinder: diameter standard
56,997 ÷ 57,025 mm (a 41 mm)
Maximum allowable runout:
0,05 mm
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