Connecting Rods and Pistons
6---3
D. Changing piston rings
1. Remove the piston rings with piston ring pliers 9052 46900.
Do not open the rings more than necessary. If the rings are to
be used again ensure that they are fitted in the same groove.
26--- 9
2. Clean the piston ring grooves and measure the piston ring
clearance, which must not exceed
0,15 mm
. Determine
whether too large a clearance is due to worn rings or a worn
groove. Change worn parts.
26--- 10
3. Measure the piston ring gap by pushing one piston ring at
a time into the cylinder bore. The piston ring gap must not ex-
ceed
1 mm
on 1. and 3. piston rings and
1,5 mm
on 2. piston
ring.
4. Fit the piston rings on the piston using the piston ring pliers.
Ensure that the rings are fitted in the correct groove and that
”TOP”, or the manufacturer’s designation, faces upwards.
26--- 11
E. Checking pistons
Check the condition of the pistons and piston pins. Pay
special attention to possible cracks on the edge of the com-
bustion chamber and on the upper edge of the piston pin
hole. Measure the diameter of the piston at the point shown
in the figure below. Renew a piston if needed.
26--- 12
634:
320, 420,
620:
