0305487 JOHNSON SEAL,Throttle gear

(A) Governor linkage (B) Throttle stop screw (C) Stop1. Disconnect linkage (A).2. Turn the throttle stop screw (B) counterclockwise until the throttle plate will close without the screw touching the stop (C).3. Turn screw (B) until it touches stop (C) with the throttle plate closed.4. With the governor lever in the OFF position and the throttle plate closed, adjust the linkages and reconnect them. (If additional linkage adjustment is necessary, contact your Caterpillar dealer.)5. Adjust the linkages so that both throttle plates open simultaneously.Carburetor Adjustments
(A) Idle adjustment screw (B) Power mixture screw (C) Throttle stop screw1. Set the power mixture screw (B) midway between "L" and "R". Make fuel mixture adjustments by changing the gas pressure from the line pressure regulator.2. Turn the idle adjustment screw (A) clockwise all the way in, then back out the adjustment screw four turns.3. Turn the throttle stop screw (C) to obtain recommended idle speed. See FUEL SETTING INFORMATION for low idle rpm.4. Do this adjustment on both carburetors.Gas Line Pressure
Gas line pressure must be regulated for use in engines. Naturally aspirated engines, using a line pressure regulator, require line pressure of 3 to 20 PSI (20 to 140 kPa). A turbocharged engine must have greater working pressure available; 12 to 20 PSI (85 to 140 kPa). 40 PSI (280 kPa) is the maximum line pressure which the fuel gas regulator can reduce to a working pressure. If gas pressure exceeds 40 PSI (280 kPa), a second regulator must be used.Line Pressure Regulator
The line pressure regulator requires adjustment when the engine is installed, when the regulator is reworked or when the heat content of the fuel is changed. A water manometer is used to set the regulator output gas pressure. Contact your Caterpillar dealer for pressure settings.1. Remove plugs (A) and (B) from the carburetor.2. Connect a water manometer and shut off valve between the two pressure taps. 3. Open the main gas valve (C).4. Increase the gas pressure with engine running to support a 5-1/2 inch (14 cm) column of water. 5. The regulator adjustment is made by removing the plug (D) and turning the slotted cap. Turn the cap clockwise to increase output pressure, or counterclockwise to decrease the pressure.Adjusting Line Pressure Regulator with Known BTU Fuel
1. With known BTU fuel, refer to a differential and BTU curve. See Form SEHS7341, or contact your Caterpillar dealer for pressure setting.2. Use the curve to find the proper differential setting which will give the correct air fuel ratio.3. Follow the procedure under LINE PRESSURE REGULATOR to obtain gas pressure that will support the proper differential, with engine at low idle condition.Adjusting Line Pressure Regulator with Unknown BTU Fuels - Variable Speed
1. Follow procedure under LINE PRESSURE REGULATOR to obtain a setting which will allow starting the engine. 2. Install an accurate tachometer on the engine.3. Remove the line regulator plug (A), and install the adjusting tool (B). On turbocharged engines, use of a special tool (B) is necessary to prevent boost pressure from escaping when regulator cap is removed.4. Start the engine and put under constant fixed load. Load should be as near full load as possible.5. Physically lock carburetor throttle plate in position while engine is operating.6. Disconnect governor linkage.7. Adjust regulator slotted cap to obtain maximum engine RPM. Maximum engine RPM can be found best by starting with a lean mixture, and slowly increasing richness to reach maximum RPM.8. Reduce the maximum obtainable RPM by 3%. This is done by leaning the mixture. Turn the slotted cap in regulator clockwise. This will give proper air fuel ratio. Each side has to be adjusted separately.9. Reconnect the governor linkage, and unlock the throttle plate.10. Remove the special tool (B) from regulator, or install cap.11. If differential is desired, a manometer may be used for this purpose.Adjusting Line Pressure Regulator with Unknown BTU Fuels - Constant Speed
1. Follow the procedure under LINE PRESSURE REGULATOR to obtain a setting which will allow starting the engine. 2. Install an accurate tachometer on the engine.3. Remove the line regulator plug (A), and install the adjusting tool (C).On turbocharged engines, use of a special tool (C) is necessary to prevent boost pressure from escaping when the regulator cap is removed.4. Read inlet manifold pressure at location (B).5. Start the engine and put it under constant fixed load. Load should be 1/2 to 3/4 rated capacity. Allow governor to keep engine at constant RPM. 6. Increase or decrease the spring tension of the regulator until the minimum inlet manifold pressure is obtained.7. After minimum inlet manifold pressure is obtained, decrease the spring pressure of regulator (turn adjusting nut counterclockwise) until inlet manifold pressure, on single carburetor engines, is increased by one inch of mercury. Increase by 1/2 inch per side on two carburetor engines.Adjusting Power Mixture Screws
The power screw is usually set at the mid-position, or 2-1/2 notches from the full lean position. Its setting will always have an effect on the adjustment of the regulator. A small adjustment of the power mixture screw will greatly change the air fuel ratio of the engine. Normally, the power mixture screw should not be changed after adjustment of the regulator. However, there are conditions that make it necessary to adjust the power mixture screw.If the spring in the regulator is backed out all the way, and the engine is still running with a too rich air-fuel mixture, turn the power screw 1/4 or 1/8notch each time until the air fuel ratio is more lean. If the power mixture screw is adjusted, the regulator must be adjusted again to the correct air fuel ratio. It is also possible to leave the regulator in a fixed position and carefully adjust the power mixture screw for a drop in RPM, or increase in inlet manifold pressure, as explained in the two adjustment procedures.After adjustment of the power screw, loads should be applied to the engine to make sure the power mixture screw is not causing poor engine operation due to a restriction