39
Group 21 Short block
Assembling the piston, piston
rings and con rod
1. Install one of the circlips in the piston.
2. Oil the gudgeon pin and con rod bush.
3. Heat the piston to approx. 100
o
C. Place the piston
and con rod so that the marks align.
The marking on the con rod and the “SHIBAURA”
marking inside the piston must face the same way.
Slide the gudgeon pin in.
NOTE! It should be possible to slide the gudgeon pin
in easily. It must not be driven in.
4. Install the other circlip.
5. Check that the con rod is not tight on the gudgeon
pin bearing.
6. Check the big end bearing clearances. Please re-
fer to “Inspecting the crankshaft” and “Inspecting
the main and big end bearings”.
7. Check the piston ring gap in the cylinder bore and
that the rings do not bind in the piston ring
grooves.
8. Install the piston rings on the pistons, using pis-
ton ring pliers. Letters or markings on ring surfac-
es must always be turned so that the marking fac-
es upwards.
Install the oil scraper ring first. Put the expansion
spring (1) for the oil scraper ring in the lower pis-
ton ring groove, with the location dowel (A) inside
both ends of the spring. Check that the ends of
the expansion spring do not overlap. Install the oil
scraper ring (2) above the expansion spring.
Check that the ring gap is displaced 180
o
from the
guide pin.
Install the ring with the tapered surface (3) in the
center piston ring pair so that the marking faces
the piston crown.
Install the upper ring (4) with the marking up-
wards.
Check that the ring gaps are displaced 90
o
from
each other.
1
2
3
4
A
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