APRILIA M192M Workshop Manual page 121

Engines M192M / M191M / M245M / M234M / M282M / M281M
• Use a suitable bore gauge to measure cylinder inner
diameter (D1 and D2) in the directions shown in the
figure. Take readings at three heights (H1, H2, and
H3).
Standard diameter:
D1 and D2= (Engines M192M / M245M / M281M) (125 cc):
Ø 56.997 ÷ 57.025 mm
D1 and D2= (Engine M191M) 150 cc: Ø 56,980 ÷ 57,008
mm
D1 and D2= (Engines M234M / M282M) (200 cc): Ø 68.990
÷ 69.018 mm
•
Check that cylinder surface mating with head is not
worn or out of shape.
Max. permitted misalignment: 0.05 mm
•
Pistons and cylinders are classified by diameter cate-
gories. Couples cylinders with pistons from the same
category (A-A, B-B, C-C, D-D).
•
Cylinders can be ground to the original angle.
•
Cylinder surface roughness must be 0.9 micron.
•
This ensures correct piston ring bedding, reduced oil
consumption and top performance.
Engines M192M / M245M / M281M / M191M (125 - 150 cc)
•
Oversized pistons for ground cylinders are available in
three categories: 1°, 2°, 3° equal to an oversize of 0.2-
0.4- 0.6 mm. Oversized pistons are also classified in 4
categories A-A, B-B, C-C, D-D.
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