November 14, 1960
Bulletin No. SB-810
Pistons & Rods
SUBJECT: Servicing Piston & Connecting Rod kit assemblies - less rings;
10 H.P. models QD-10 thru 21S.
A new piston, connecting rod, anti-friction wrist pin needle bearing and wrist pin have
been developed for use in the 1961 - 10 H.P. engines. These new parts were specifically
designed to eliminate any possibility of failure due to wrist pins loosening, part-
icularly in heavy duty application.
For 10 h.p. engines of 1960 vintage and earlier, the currently available pistons and
connecting rods, listed below, will not be serviced after the present stock of parts
is exhausted. The older wrist pins (303711 and 301788) will continue to be available
for service in those engines where only the wrist pin must be replaced. The piston
rings are the same as they have been in the past.
In servicing an engine, if you require any of the following detail parts or assemblies
and your parts distributor’s stock is exhausted, order part #378393. This part number
includes one piston, one connecting rod, one wrist pin needle bearing, one wrist pin
and two wrist pin retainers; all of which are supplied in unassembled form (knocked down)
as a kit assembly. Piston rings are not included in this kit and must be separately
ordered.
375595 - Connecting rod
376223 - Connecting rod
377044 - Connecting rod
375591 - Piston - std.
376202 - Piston - std.
377031 - Piston - std.
377032 - Piston and Wrist pin
375668 - Piston and rod assembly - upper - Std.
375730 - Piston and rod assembly - lower - Std.
376224 - Piston and Rod - upper - std.
376226 - Piston and Rod - lower - std.
377042 - Piston and Rod - upper - std.
377043 - Piston and Rod - lower - std.
NOTE: Only one 378393 knocked-down kit assembly is needed for each cylinder. Two assem-
blies are needed for one engine. These assemblies are for standard size cylinders only;
no oversize kit assemblies are available. Therefore, if you need oversize pistons and
your distributor’s supply is exhausted, please contact the factory’s service department
and state your needs. However, the current supply of oversize pistons should take care
of your needs for the next year.
The price of this new assembly (378393) is $10.00, less your regular parts discounts. It
will be available from your distributor when his supply of any of the detail parts listed
above has been exhausted.
Our engineering department has stated that both old style piston and rod assemblies need
not necessarily be replaced with two new style assemblies unless normal service would
require that this be done.
JOHNSON MOTORS
W. W. DeWees
Service Department
WWD:eb
NOTE: Post on your QD index - 10 H.P.
W. W. DeWees