April 22,1959
Service Bulletin No. SB 712
Subject: SERVICING THE RD - RDS-21 and RD - RDS - 21B POWERHEAD
In November of 1958 a model change was made on
the 1959 35 H.P. engine, from RD, RDS-21 to RD
RDS-21B. The changes made indicated by the
letter "B" of the model designation, were to the
crankshaft, connecting rod, wrist pin bearing
and connecting rod retainer and needles.
Pictured are the changes. When ordering the above
listed parts for service on the 1959 35 HP engine,
determine the exact model, from the serial number
plate. When referring to your parts catalog you
will note the parts required for the model 21B
are identified with an asterisk (*) to the right
of the item number. The parts required for the
model 21 have the same item number but are not
marked with an asterisk.
In order that there will be no delay in repairs,
due to ordering of incorrect parts, be certain
the exact model is determined before ordering.
NOTE: The early crankshafts for the model
21B, as pictured, can be identified by an
increased radius on the connecting rod journal
as indicated by the arrow. The crankshaft
presently being produced are identified by
etching the part number on the crankshaft
flywheel taper.
JOHNSON MOTORS
Jack Penland
Jack Penland
Service Department
JP:eb