Figure 6-34. Pressing in New Piston Pin Bearings
spring scale into the end of the feeler ribbon and pull the
feeler ribbon from the cylinder. If the fit is correct, the
scale should register 5 to 10 pounds pull.
e. Piston pin fit. Check the fit of the piston pin in
Figure 6-33. Piston and Rod Assembly
piston and the connecting rod. The piston pin should
be a thumb push fit ii the piston pin bearing and a palm
(1) Soak pistons in SD and remove carbon
push fit in the piston bosses. If the piston pins or
from the tops and from ring grooves of the pistons.
bearings are worn, they must be replaced with standard
(2) Using a drill or probe of the proper size,
size pins and bearings. If the piston bosses are worn,
clean carbon from the oil return holes in the ring grooves.
the piston must be replaced.
(3) Clean the oil groove passages in the
f. Piston ring installation.
connecting rods and caps.
(1) Always install new piston rings during an
d. Piston fit. Fit the pistons clean and dry. To fit
overhaul of the engine. Replacement rings are available
the pistons to the cylinder bore properly, use a spring
in standard size, in 0.020 inch oversize, and in 0.040 inch
scale and a feeler ribbon 1/2 inch wide, 10 inches long,
and 0.003 inch thick (Figure 6-35). Insert the feeler
(2) To determine whether the ring has the
ribbon full length into the cylinder bore, about halfway
proper end gap, place it in the cylinder, pushing it about
down. Hook the
halfway down in the cylinder bore. With the ring square
with the cylinder
Figure 6-35. Measuring Piston Fit in Cylinder