- 29 -
26
24
25
27
4
STD mm - 0,25 mm - 0,50 mm -0,75 mm
A - B - D
45,005
÷
45,015
44,755
÷
44,765
44,505
÷
44,515
44,255
÷
44,265
C
39,994
÷
40,010
39,744
÷
39,760
39,494
÷
39,510
39,244
÷
39,260
Checks and overhaul
2. Position the calibrated pin on two prisms arranged on a
check surface.
3. Use a dial gauge to check that the discrepancy between
readings at the ends of the calibrated pin is no more than
0.05 mm; should deformation exceed this value (max.
0.10mm) the connecting rod must be straightened.
This operation is performed by placing the connecting rod
on a parallel surface and applying slight pressure mid-way
along the convex side of the stem (g.24).
Crankshaft
Whenever the engine is dismantled, particularly for the
replacement of cylinders and pistons due to wear caused by the
aspiration of dust, it is good practice to check the condition of the
crankshaft.
1
. Remove the plugs “A” from the oil passages (g.25).
2. Use an appropriately shaped steel punch to clean the inside
of the oil passages and the collection traps. If the deposits
are particularly resistant, immerse the whole crankshaft in
petrol or parafn before proceeding with the operations.
3. When the oil passages and traps have been throughly
cleaned, close the openings with new plugs (g.26).
Checking crankshaft dimensions
Once the crankshaft has been thoroughly cleaned, use a
micrometer to check the wear and ovality of the main journals
and crank journals across two sections at right angles to each
other (g.27).
If wear exceeds 0.08 mm (g.28) grind the crankshaft to the
dimensions shown in the table:
Undersize bearing bushes are already available at the
necessary sizes without requiring any adjustment by boring.
Dimensions
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