Johnson Service Bulletin SB-982 Revision 1 - Orifice Plug Chart
Issued February 1965, this revision identifies fixed and adjustable high-speed carburetor orifice plugs, their engine applications, and the factory identifying marks. The original four-page bulletin is reproduced below.
February, 1965
SUBJECT: ORIFICE PLUG (HIGH SPEED JET) CHART.
ON ENGINES: ALL MODELS
All current, as well as non-current, carburetor orifice plugs are listed here along with their identifying characteristics and their recommended usage. The illustrations below show the two different thread types that are used.
| ENGINE MODEL NUMBER | H.P. | ORIFICE PLUG PART NUMBER | ORIFICE PLUG IDENTIFICATION |
|---|---|---|---|
| JW-18R | 3 | 309345 | Stamped #29 or #30; Full thread.¹ |
| JW & JH-19A, 19M, & 20B | 3 | 310758 | Stamped #28 or #29; Full thread.¹ |
| LD-10S | 5 | 311854 | Stamped #41; Full thread. |
| CD-21A | 5½ | 309389 | Stamped #40; Full thread. |
| CD-22M | 6 | 311854 | Stamped #41; Full thread. |
| MQ-10R, 10S & 11C | 9½ | 309681 | Stamped #48 or #52; Full thread.⁵ |
| FD-18E & 19D | 18 | 309415 | Stamped #64; Full thread. |
| RD & RDS-23 | 40 | 307781 | One groove on long end; one groove on short end; Short thread. |
| RD & RDS-24, 24B, 24M, & 24L | 40 | 307813 | One groove on short end; Short thread. |
| ENGINE MODEL NUMBER | H.P. | ORIFICE PLUG PART NUMBER | ORIFICE PLUG IDENTIFICATION |
|---|---|---|---|
| RD-25D | 40 | 309935 | Stamped #68; Full thread. |
| RD & RDS-26R & 26S, 27A & 27M | 40 | 309415 | Stamped #64; Full thread. |
| RK-24, 24B & 24L | 40 | 307813 | One groove on short end; Short thread. |
| RK-25D | 40 | 309935 | Stamped #68; Full thread. |
| RK-26R | 40 | 309415 | Stamped #64; Full thread. |
| RK-26S | 40 | 309935 | Stamped #68; Full thread. |
| RK-27A | 40 | 309415 | Stamped #64; Full thread. |
| V4 & V4S-10, 10H, 11 & 11B | 50 | 307065 | Plain; Short thread. |
| V4S-12 & 12S | 75 | 307532 | One groove on long end; Short thread. |
| V4S-13 & 13C | 75 | 307813 | One groove on short end; Short thread. |
| V4S-14, 14B, 15C, 15R, 15S & 16A | 75 | 309517 | Stamped #72; Full thread. |
| VX-10S, 11A & 11C | 60 | 554049 | Two grooves on long end; Short thread. |
| VXH-10S, & 11C | 60 | 554049 | Two grooves on long end; Short thread. |
| V4A-13, 13C & 13F | 75 | 307813 | One groove on short end; Short thread. |
| V4A-14, 14M, 14L, 15E, 16D & 17S | 75 | 309517 | Stamped #72; Full thread. |
| V4H-16A & 17S | 75 | 309517 | Stamped #72; Full thread. |
| DU-10S | 80 | 308977 | Stamped #52, #57, or #58; Full thread.⁴ |
| DU & DUE-11A | 88 | 308977 | Stamped #52, #57, or #58; Full thread.⁴ |
| DU-12M | 90 | 308977 | Stamped #52, #57, or #58; Full thread.⁴ |
| ENGINE MODEL NUMBER | H.P. | ORIFICE PLUG PART NUMBER | ORIFICE PLUG IDENTIFICATION |
|---|---|---|---|
| DUE-12M | 90 | 308977 | Stamped #52, #57 or #58; Full thread.⁴ |
| V4M-10A | 90 | 311530 | Stamped #70; Full thread.² |
| V4M-10R & 10S | 90 | 309935 | Stamped #68; Full thread.³ |
| V4M-11C | 90 | 311530 | Stamped #70; Full thread.² |
The following orifice plugs are used in adjustable high speed jet accessory kits. Note that here, the part number of the accessory kit in which the respective orifice plug is used has also been given.
| ENGINE MODEL NUMBER | H.P. | ORIFICE PLUG PART NUMBER | ORIFICE PLUG IDENTIFICATION | ACCESSORY KIT PART NUMBER |
|---|---|---|---|---|
| JW-18 thru 18R | 3 | 310575 | Stamped A34; Full thread. | 379627 |
| JW & JH-19A thru 20B | 3 | 310575 | Stamped A34; Full thread. | 379627 |
| RD-23 | 40 | 309790 | Stamped A74; Full thread. | 379188 |
| RD & RK-24 thru 27M | 40 | 309790 | Stamped A74; Full thread. | 379188 |
| V4S & V4A-13 thru 17S | 75 | 309790 | Stamped A74; Full thread. | 379189 |
NOTES
- Only orifice plugs stamped #29 should be used in JW & JH engines using fixed high speed jets. (See SB-#1025, Rev. 1).
- Use only in the following carburetors:
- Those carburetors with only one float bowl gasket and no other identifying marks.
- Those carburetors using two float bowl gaskets and a stainless steel plate between the two float bowl gaskets.
- Use only in carburetors with an orange letter "M" stamped on top which uses only one float bowl gasket.
- Only orifice plugs stamped #58 should be used in these DU & DUE engines.
- Only orifice plugs stamped #48 should be used in MQ engines.
N. Peter Hansen
Administrative Assistant
NPH:rs
NOTE: Post on all indexes under "Carburetion."
Destroy bulletin SB-982, dated October 10, 1963.