Chapter 8 – Cylinder and Piston
Service Manual AJP PR3/PR4 8 - 7
However, it is recommended that the cylinder
always be replaced together with the piston,
rings and piston pin with circlips
Then measure the outer diameter of the
piston pin. Also check their appearance if is
scratched or bluish. If so, replace the piston
and the pin, and check the lubrication system.
Service limit
125cm
3
14,96mm
200/240cm
3
17,96mm
Measure also the internal diameter of the
cavity of piston pin in the piston housing,
using the maximum value found for
comparison with the specified service limit. If
exceeded this limit, the piston must be
replaced along with the respective pin.
Service limit
125cm
3
15,04mm
200/240cm
3
17,04mm
Finally, in this control, calculation of the
clearance between the pin and the respective
pin housing in piston cavity must be made,
confirming also in this case if the clearance
respect the specified service limit.
Service limit of the clearance between
cavity / piston pin:
0,02mm
Then inspect the piston rings on the
smoothness of movement. If they are
obstructed they should be cleaned.
Subsequently, with the help of a feeler gauge,
measure the clearance of the ringsin their
cavities in the piston housing.
Note:
Eliminate any type of coal in the ring
cavities to avoid any incorrect measures.
Service
limit
Top segment
0,09mm
Secondary
segment
0,08mm
Install piston rings, each one at a time, inside
cylinder using the piston head to place rings
leveled.
Measure the clearance in the rings ends with
the help of a blade gauge as shown in
following picture.
If clearance is out of specified limits, rings
Service
limit
Top segment
0,5mm
Secondary
segment
0,65mm
Oil segment
(rail side)
0,9mm
Connecting rod
Note:
Whenever it is verified that the service
limit of the piston pin or pin housing cavity in