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Disassembly, Cleaning and Repair of Briggs and Stratton Tank-mounted Pulsa-jet Adjustable Carburetor - Horizontal Crankshaft Engine

Briggs carb part numbers 296784, 296882, 296905, 296927, 296968, 297153, 297223, 297599, 297680, 297918, 298547, 299185, 299278, 299437, 299488, 299576, 392894, 392905, 393975, 393976, 394083, 394084, 394085, 394828, 393977, 396748, 397135, 397939, 398049, 398124, 398711, 399633
used on Briggs and Stratton Engines 060201, 060202, 060206, 060211, 060212, 060231, 060232, 060251, 060252, 061201, 061202, 061211, 061212, 061231, 061232, 061251, 061252, 080201, 080202, 080203, 080206, 080211, 080212, 080213, 080216, 080231, 080232, 080233, 080236, 080251, 080252, 080253, 080256, 080291, 080292, 080296, 081201, 081202, 081203, 081206, 081211, 081212, 081213, 081216, 081231, 081232, 081233, 081236, 081251, 081252, 081253, 081256, 081292, 081296, 082212, 082231, 082232, 082252, 090202, 090212, 090232, 090252, 091202, 091212, 091232, 091252, 100201, 100202, 100212, 100231, 100232, 100251, 100252, 100292, 100900, 100902, 100992, 111202, 111212, 111231, 111232, 111252, 111292, 112201, 112202, 112212, 112231, 112232, 112252, 112292, 113908, 130201, 130202, 130203, 130205, 130206, 130207, 130212, 130217, 130231, 130232, 130233, 130235, 130236, 130237, 130251, 130252, 130253, 130292, 130293, 130296, 130297, 130902, 130903, 130905, 130907, 130982, 130992, 131212, 131231, 131232, 131237, 131251, 131252, 131292, 131922, 132212, 132213, 132231, 132232, 132235, 132237, 132251, 132252, 132292, 132297, 132922, 132925, 132927, 132982, 132992, 140201, 140202, 140231, 140232, 140251, 140252, 141201, 141202, 141204, 141207, 141231, 141232, 141251, 141252, 144201, 144202, 144231, 144232, 144251, 144252, 145201, 145202, 145231, 145232, 145251, 145252

Quick notes:
The preset (preliminary adjustment) for the needle valve is 1-1/2 turns out from lightly seated.
The carburetor and fuel tank are removed from the engine together as a unit.
Besides dirt, the main problem with this carb would be a worn out diaphragm.

#1. Briggs Pulsa-jet Adjustable Carburetor - Horizontal Crankshaft
The Briggs and Stratton Tank-mounted Pulsa-jet Adjustable carburetor shown here can be identified, without removing the carb from the tank, by the presence of the fuel pump on the side of the carb and the needle valve directly adjacent to the throttle plate. This carb is used on engines with horizontal crankshafts.
#2. Manual rotary choke
This carb has a manually operated rotary type choke (#2).
#3. Choke shaft and choke plate snap together
The choke shaft and choke plate snap together (#3). Press outward with a screwdriver to separate them.
#4. Remove choke plate
After removing the choke shaft the choke plate can be tilted and lifted out (#4).
#5. Plastic choke plate and shaft
The choke plate and shaft used on this rotary choke are plastic and snap together (#5).
#6. Throttle linkage
A typical remotely controlled throttle linkage (#6).
#7. Remote slide choke
This adjustable carb is equipped with a remotely controlled slide type choke (#7).
#8. Choke slide
The choke slide is held in place by a rivet (#8). There is nothing to clean or service by removing the slide.
#9. Typical slide choke and throttle linkages
Typical slide choke and throttle linkages (#9).
#10. Fuel pump intake
Fuel begins its journey in the fuel tank and is drawn into the longer fuel pickup tube by the fuel pump. A wire inserted into the hole where the longer fuel pickup tube was removed shows the passage to the upper hole in the pump (#10).
#11. Diaphragm spring and cup
The diaphragm spring cup protects the diaphragm from damage by the spring (#11). Vacuum pulsations from the engine intake draw in the diaphragm and the spring pushes it back.
#12. Diaphragm flapper valves
Those little tabs on the diaphragm act as flapper check valves allowing fuel to flow only one direction (#12). The in and out motion of the diaphragm in concert with the flapper valves cuases fuel to flow through the pump.
#13. Fuel flow through pump cover
Fuel flows past the first flapper into a recess in the pump cover and out past the second flapper valve (#13).
#14. Fuel pump output
Fuel passes out past the second flapper valve (#14) and into a well on the fuel tank (shown with long tube removed). Excess fuel in the well overflows into the main part of the fuel tank thus maintaining a constant level of available fuel .
#15. Short fuel pickup tube
The shorter fuel pickup tube picks up fuel from the reservoir in the tank and delivers it to the needle valve (#15). Use a 3/8 inch box wrench to unscrew it from the carb. Both pickup tubes have wire mesh screens to keep out dirt.
#16. Fuel mixture needle valve
The fuel mixture needle valve is located directly alongside the throttle plate (#16) and meters fuel for both the high and low idle. The initial setting is 1-1/2 turns out from lightly seated.
#17. Fuel mixture needle valve
An exploded view of the mixture needle valve and seat (#17). Check the needle tip for a straight smooth taper. When re-installing the assembly, screw in the needle valve nut and then screw in the needle so as to avoid jamming the needle into the seat.
#18. Needle valve seat
The mixture needle seat is brass and can be unscrewed for cleaning or replacement (#18).
#19. High and low discharge ports
The needle valve meters fuel to both the high and low idle fuel discharge ports (#19). The smaller one to the right is located just at the throttle closed position and supplies fuel at both high and low speed. The larger one to the left is the main fuel discharge port and supplies fuel only at open throttle.
#20. Main fuel discharge port location
A wire shows the location of the main fuel discharge port relative to the throttle plate (#20).
#21. Cast throttle plate
Both sides of a cast throttle plate are shown (#21). The raised tab aligns to the metering holes and toward the engine block.
#22. Throttle plate alignment
The tab on the throttle plate is aligned toward the metering holes (#22) with the raised tab to the engine side of the carb.
#23. Spiral in throat
Some carbs have a spiral downstream of the throttle to help mix the fuel and air (#23). It can be removed by pulling it with pliers and a moderate twisting motion. It is installed so that its end is flush to 1/32 inch below the carb to engine mounting flange and parallel to the carb to fuel tank interface surface.
#24. Mixing spiral
The spiral is held in place only by a tight fit. It consists of one half twist with ends parallel to each other (#24) .
#25. Breather opening
Gases that exit the crankcase breather are recirculated into the carb through the breather opening (#25, yellow) to reduce pollution. A large welch plug seals the carb elbow (#25, blue). The plug can be popped out from the inside with a screwdriver and a sharp blow, but there is nothing to clean or service behind it.
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