Specifications

cylinder bore. Check gap with feeler gauge (Fig. 77).
Top compression ring gap .25 to .50 mm (.0098 to
.0196 in.). Second compression ring gap .25 to .35
mm (.0098 to .0137 in.). Oil control ring gap .25 to
.58 mm (.0098 to .0228 in.).
(2) If ring gaps exceed dimension given, new rings
or cylinder liners must be fitted. Keep piston rings in
piston sets.
(3) Check piston ring to groove clearance (Fig. 78).
Top compression ring gap .08 to .130 mm (.0031 to
.0051 in.). Second compression ring gap .070 to .102
mm (.0027 to .0040 in.). Oil control ring gap .040 to
.072 mm (.0015 to .0028 in.).
PISTON RINGS—INSTALLATION
(1) Install rings on the pistons using a suitable
ring expander (Fig. 76).
(2) Top compression ring is tapered and chromium
plated. The second ring is of the scraper type and
must be installed with scraping edge facing bottom of
the piston. The third is an oil control ring (Fig. 79).
Ring gaps must be positioned, before inserting piston
into the liners, as follows (Fig. 80).
(3) Top ring gap must be positioned at 30 degrees
to the right of the combustion chamber recess (look-
ing at the piston crown from above).
(4) Second piston ring gap should be positioned on
the opposite side of the combustion chamber recess.
(5) Oil control ring gap to be located 30 degrees to
the left of combustion chamber recess.
(6) When assembling pistons check that compo-
nents are installed in the same position as before dis-
assembly, determined by the numbers stamped on
the crown of individual pistons. Engine cylinders are
numbered starting from gear train end of the engine.
Face chamber recess side of piston towards
camshaft . Therefore, the numbers stamped on con
Fig. 76 Piston Rings—Removing and Installing
Fig. 77 Ring Gap Measurement
Fig. 78 Piston Ring Side Clearance
Fig. 79 Piston Ring Identification
NS/GS ENGINE 9 - 69
REMOVAL AND INSTALLATION (Continued)