Page 420 - Foton Workshop Manual - Aumark (BJ1099)

12B-130 ENGINE MECHANICAL - PISTON AND CONNECTING ROD

4. Check the diameter of the piston
(a). Check and measure the diameter of the
piston as shown in the fig.
(b). Compare and check the diameter of the
piston according to the letter identification
on the top of the piston and the table
below.

Letters Standard piston diameter(mm)

A 85.95~85.96
B 85.96~85.97

C 85.97~95.98

• If the diameter of the piston does not conform to
the standard diameter, replace the piston.
5. Calculate the clearance between the piston and the cylinder

(a). Check the diameter of the cylinder bore.(Refer To"Chapter 12B Engine Mechanical
Systerm- Cylinder Block,Checking")
Computing method:
The clearance between the piston and the cylinder = the diameter of the cylinder
bore - the diameter of the piston
Standard value:0.04~0.06mm

• If the clearance between the piston and the cylinder does not conform to the
standard clearance, replace the piston,and bore or replace the cylinder if
necessary.

6. Check the oil clearance of the piston pin

(a). Measure the diameter of the mounting hole
on the piston pin.

(b). Check the excircle diameter of the piston
pin.

(c). The diameter of the mounting hole on the
piston pin - the excircle diameter of the
piston pin = the oil clearance between the
piston and the piston pin.

NOTICE:
If the oil clearance is greater than the clearance
value, replace the piston pin, and replace the
piston if necessary.

Page 420