And Pistons - Evinrude 4906B 4HP 1969 Owner's Manual

critical during inspection
been submerged.
Carefully check each wrist pin to be sure
it is not the least bit bent.
bent, the pin and piston
as a set, because the pin will have damaged
the boss when it was removed.
Check the wrist pin bearings.
bearing is the pressed-in
finger and determine
condition with no indication
"rough" spots. If the wrist pin bearing is the
removable type, the needle should be re-
placed.
Grasp each end of the ring with either a
ring expander or your thumbnails,
ring and remove it from the piston.
times, the ring may be difficult
because it is "frozen"
groove. In such a case, use a screwdriver
and pry the ring free.
but if it is difficult
replaced.
OBSERVE the pin in each ring groove of
the piston. The ends of the ring
straddle this pin. The pin prevents the ring
from rotating while the engine is operating.
This fact is the direct opposite of a four-
cycle engine where the ring must rotate.
a two-cycle engine, if the ring is permitted
to rotate, at one point, the opening between
the ring ends would align with either
intake or exhaust port in the cylinder.
Piston badly scored and
if the engine has
If a wrist pin is
MUST be replaced
If the
type, use your
the bearing is in good
of binding or
open the
Many
to remove
in the piston ring
The ring may break,
to remove, it MUST be
MUST
no
longer fit for service.
Close view
groove.
that time,
slightly, catch on the edge of the port, and
BREAK.
Therefore,
In of the piston,
each groove to be sure it is tight.
is the least bit loose, the piston
the replaced, without question.
At to replace the pin, it is NEVER successful.
Removing the rings from the piston.
RODS

AND PISTONS

of a
piston showing the ring pin in the
the ring would expand
when checking the condition
check the pin in
AL WAYS
Never attempt
3-23
very
If one pin
MUST be