Johnson Service Bulletin SB-988 - Carburetor Cam Follower Roller

October 22, 1963. Factory guidance on the improved nylon carburetor cam follower roller 310354 for V4 engines, with original old and new roller comparison photographs.

Johnson Motors gray service bulletin header
SB-# 988
October 22, 1963
SUBJECT: Part No. 310354 ROLLER - Carburetor Cam Follower.
For Engines: 50 H.P. - V4(L)-10 thru 11B V4S(L)-10 thru 11B 60 H.P. - VX(L)-10S 75 H.P. - V4S(L)-12 and up V4A(L)-13 and up 90 H.P. - V4M(L)-10S
The carburetor cam follower roller as used on V4 series engines has recently been improved. The part number of the improved roller has been changed and is now listed as service part #310354.
Factory photograph identifying carburetor cam follower on V4 engine
At present, only some 1964-V4 series engines include part #310354, however, future planning will eventually include adding this part to all production V4 models. Characteristics of this new roller that make its design superior to the part used pre- viously in this application are: 1) one piece design, 2) nylon construction for more durability, 3) resistance to flattening or grooving from contact with cam, 4) affords smoother linkage operation and 5) improved concentricity permits more accurate synchronization of carburetor and magneto.
Showing carburetor cam follower as employed on V4 series engines - 50 through 75 H.P.
This new nylon roller will be used for service on all V4 engines (50 thru 90 H.P.), in place of parts #304862 ROLLER and #305233 BUSHING. Part #304862 has usage other than on V4 engines and will be maintained as service replacement for these applications. Part #305233 has no usage other than its application on V4 engines and will therefore be superseded shortly by #310354.
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SB-# 988 Page 2
Original old-style three-piece carburetor cam follower photographOriginal new-style one-piece carburetor cam follower photograph
Showing old style three piece carburetor cam follower.
Showing new style one piece carburetor cam follower.
In summary - if evidence of wear on the cam follower roller is noted when servicing any V4 engine, replace the old roller and bushings with the new nylon roller.
Part No. 310354 is presently available from your Parts Distributor at the suggested list price of $.05 each. Your standard parts discount (36%) applies.
Sincerely, JOHNSON MOTORS R. Compton Administrative Assistant
RC:eb
NOTE: Post on your V4 - 50 H.P., V4 - 60 H.P., V4 - 75 H.P. and V4 90 H.P. Indexes.