Johnson Service Bulletin SB-982 Rev. 2 - Orifice Plug Chart
Issued September 1965, this four-page Johnson Motors reference lists high-speed carburetor orifice plugs for current and earlier engine models. The original factory chart, identification markings and five footnotes are reproduced as searchable text below.
September, 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.
You will please note, that in some instances, orifice plugs for a particular engine model have been produced in two different sizes, although the same part number was used for both orifice plug sizes. If you order the part number corresponding to the particular engine model that you want an orifice plug for, you will receive the orifice plug size that is currently recommended.
In cases where more than one orifice plug size was produced under the same part number, there are footnotes which tell which orifice plug is currently recommended.
| 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, & 21E | 3 | 310758 | Stamped #28 or #29; Full thread.1 |
| LD-10S, & 11C | 5 | 311854 | Stamped #41; Full thread. |
| CD-21A | 5½ | 309389 | Stamped #40; Full thread. |
| CD-22M, & 23B | 6 | 311854 | Stamped #41; Full thread. |
| ENGINE MODEL NUMBER | H.P. | ORIFICE PLUG PART NUMBER | ORIFICE PLUG IDENTIFICATION |
|---|---|---|---|
| MQ-10R, 10S, 11C, & 12A | 9½ | 309681 | Stamped #48 or #52; Full thread.5 |
| FD-18E, 19D | 18 | 309415 | Stamped #64; Full thread. |
| FD-20C | 20 | 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. |
| RD-25D | 40 | 309935 | Stamped #68; Full thread. |
| RD & RDS-26R, 26S, 27A, 27M, & 28B | 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, & 28B | 40 | 309415 | Stamped #64; Full thread. |
| V4 & V4S-10, 10H, 11 & 11B | 50 | 307065 | Plain; Short thread. |
| VX-10S, 11A, 11C | 60 | 554049 | Two grooves on long end; Short thread. |
| VX-12R | 60 | 309517 | Stamped #72; Full thread. |
| VXH-10S, 11C | 60 | 554049 | Two grooves on long end; Short thread. |
| VXH-12R | 60 | 309517 | Stamped #72; Full 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. |
| ENGINE MODEL NUMBER | H.P. | ORIFICE PLUG PART NUMBER | ORIFICE PLUG IDENTIFICATION |
|---|---|---|---|
| V4S-14, 14B, 15C, 15R, 15S & 16A | 75 | 309517 | Stamped #72; Full 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. |
| V4S-18C | 80 | 309415 | Stamped #64; Full thread. |
| V4A-18C | 80 | 309415 | Stamped #64; Full thread. |
| DU-10S | 80 | 308977 | Stamped #52, #57, or #58; Full thread.4 |
| DU-11A, 11C, & 11R | 88 | 308977 | Stamped #52, #57, or #58; Full thread.4 |
| DUE-11A | 88 | 308977 | Stamped #52, #57, or #58; Full thread.4 |
| DU-12M | 90 | 308977 | Stamped #52, #57, or #58; Full thread.4 |
| 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 |
| V4ML-12R | 100 | 312226 | Stamped #65; Full thread. |
- FOOTNOTES -
- Refer to SB-1025 Rev. 1 dated November, 1964.
- 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 of the automatic choke assembly. This carburetor uses only one float bowl gasket.
- Only orifice plugs stamped with a #58 should be used in these DU & DUE engines.
- Only orifice plugs stamped with a #48 should be used in these MQ engines.
N. Peter Hansen
Administrative Assistant
NPH:rs
NOTE: Post on all indexes under "Carburetion".
Destroy bulletin SB-#982 Rev. 1 dated February, 1965.
Historical references
Related bulletin: SB-1025 Rev. 1 (November 1964). This revision supersedes SB-982 Rev. 1 (February 1965).
Factory jet part numbers indexed in this chart: 307065, 307532, 307781, 307813, 308977, 309345, 309389, 309415, 309517, 309681, 309935, 310758, 311530, 311854, 312226, 554049.
Factory recommendations are historical and should be checked against the applicable engine and carburetor before use.