Carburetors having filter arrangements

Abstract

A carburetor has a carburetor body having a venturi passage that conveys air from an air inlet to an air outlet. A throttle valve controls flow of the air in the venturi passage. The throttle valve is movable into a closed position, an open position, and at least one transition position between the closed position and the open position. A fuel bowl holds fuel for mixing with the air in the venturi passage. A main nozzle discharges the fuel from the fuel bowl to the air in the venturi passage when the throttle is in the open position. A secondary circuit that is smaller than the main nozzle discharges fuel from the fuel bowl to the air in the venturi passage when the throttle is in the closed position, the transition position, and the open position. A filter is configured to remove particulate matter from the fuel in the fuel howl prior to discharge via the secondary circuit. Methods are for making the carburetor and operating the carburetor.

What is claimed is: 
     
       1. A carburetor comprising:
 a carburetor body having a venturi passage that conveys air from an air inlet to an air outlet; 
 a throttle valve that controls flow of the air in the venturi passage, wherein the throttle valve is movable into a closed position, an open position, and at least one transition position between the closed position and the open position; 
 a fuel bowl that holds fuel for mixing with the air in the venturi passage; 
 a main nozzle that discharges the fuel from the fuel bowl to the air in the venturi passage when the throttle valve is in the open position; 
 a secondary circuit that discharges fuel from the fuel bowl to the air in the venturi passage when the throttle valve is in the closed position, the transition position, and the open position; 
 a filter that is configured to remove particulate matter from the fuel in the fuel bowl prior to discharge via the secondary circuit; 
 wherein the filter is located externally of the fuel bowl; and 
 wherein the fuel bowl has an outlet passage that drains the fuel from the fuel bowl and an inlet passage that conveys the fuel from the outlet passage to the secondary circuit, wherein the filter is located downstream of the outlet passage and upstream of the inlet passage. 
 
     
     
       2. The carburetor according to  claim 1 , further comprising a removable cap on the filter. 
     
     
       3. The carburetor according to  claim 1 , further comprising a secondary jet that supports the secondary circuit, wherein the secondary jet has a through-bore that conveys the fuel from the inlet passage to the secondary circuit. 
     
     
       4. The carburetor according to  claim 3 , wherein the secondary jet has an inlet end that is sealed to an interior surface of the fuel bowl. 
     
     
       5. A carburetor comprising:
 a carburetor body having a venturi passage that conveys air from an air inlet to an air outlet; 
 a throttle valve that controls flow of the air in the venturi passage, wherein the throttle valve is movable into a closed position, an open position, and at least one transition position between the closed position and the open position; 
 a fuel bowl that holds fuel for mixing with the air in the venturi passage; 
 a main nozzle that discharges the fuel from the fuel bowl to the air in the venturi passage when the throttle valve is in the open position; 
 a secondary circuit that discharges fuel from the fuel bowl to the air in the venturi passage when the throttle valve is in the closed position, the transition position, and the open position; 
 a filter that is configured to remove particulate matter from the fuel in the fuel bowl prior to discharge via the secondary circuit; 
 wherein the filter is located inside the carburetor body; and 
 a main jet having a through-bore that conveys fuel from fuel bowl to the main nozzle, and 
 a secondary jet having a through-bore that conveys fuel from the main nozzle to the secondary circuit, 
 wherein the filter is located downstream of the through-bore of the main jet and upstream of the through-bore of the secondary jet. 
 
     
     
       6. The carburetor according to  claim 5 , wherein a passageway extends between the through-bore of the main jet and the through-bore of the secondary jet, and wherein the filter filters fuel that flows through the passageway. 
     
     
       7. The carburetor according to  claim 6 , wherein the filter comprises a filter media that is between the main jet and the main nozzle. 
     
     
       8. The carburetor according to  claim 6 , wherein the filter comprises a plurality of fuel holes that are circumferentially spaced around the main nozzle, each fuel hole in the plurality of fuel holes having a size that is small enough to prevent passage of particulate matter that would otherwise restrict fuel from flowing through the secondary circuit. 
     
     
       9. The carburetor according to  claim 8 , wherein the main nozzle comprises an elongated element having first and second ends, wherein the first end receives the fuel from the main jet and wherein the second end discharges the fuel to the venturi passage in the carburetor body. 
     
     
       10. The carburetor according to  claim 9 , wherein the main nozzle comprises an outer circumference and an inner passageway extending from the first end to the second end, and wherein the plurality of fuel holes are disposed around the outer circumference at the first end, and wherein each fuel hole extends through the elongated element from the outer circumference to the inner passageway. 
     
     
       11. The carburetor according to  claim 10 , wherein the elongated element further comprises a plurality of air holes that are configured to aerate the fuel in the main nozzle, wherein the plurality of fuel holes are located closer to the first end than the plurality of air holes. 
     
     
       12. The carburetor according to  claim 11 , wherein the elongated element further comprises a flange located between the plurality of fuel holes and the plurality of air holes, and wherein the flange is configured to stabilize the main nozzle with respect to the carburetor body. 
     
     
       13. A method of making a carburetor, the method comprising:
 providing a carburetor body having a venturi passage that conveys air from an air inlet to an air outlet; 
 providing a throttle valve that controls flow of the air in the venturi passage, wherein the throttle valve is movable into a closed position, an open position, and at least one transition position between the closed position and the open position; 
 providing a fuel bowl that holds fuel for mixing with the air in the venturi passage; 
 providing a main nozzle that discharges the fuel from the fuel bowl to the air in the venturi passage when the throttle is in the open position; 
 providing a secondary circuit that discharges fuel from the fuel bowl to the air in the venturi passage when the throttle is in the closed position, the transition position, and the open position; 
 providing a filter that is configured to remove particulate matter from the fuel in the fuel bowl prior to discharge via the secondary circuit; and 
 locating the filter externally of the fuel bowl, wherein the fuel bowl has an outlet passage that drains the fuel from the fuel bowl and an inlet passage that conveys the fuel from the outlet passage to the secondary circuit, and further comprising locating the filter downstream of the outlet passage and upstream of the inlet passage. 
 
     
     
       14. A method of making a carburetor, the method comprising:
 providing a carburetor body having a venturi passage that conveys air from an air inlet to an air outlet; 
 providing a throttle valve that controls flow of the air in the venturi passage, wherein the throttle valve is movable into a closed position, an open position, and at least one transition position between the closed position and the open position; 
 providing a fuel bowl that holds fuel for mixing with the air in the venturi passage; 
 providing a main nozzle that discharges the fuel from the fuel bowl to the air in the venturi passage when the throttle is in the open position; 
 providing a secondary circuit that discharges fuel from the fuel bowl to the air in the venturi passage when the throttle is in the closed position, the transition position, and the open position; 
 providing a filter that is configured to remove particulate matter from the fuel in the fuel bowl prior to discharge via the secondary circuit; and 
 locating the filter inside the carburetor body, and further comprising providing a main jet having a through-bore that conveys fuel from fuel bowl to the main nozzle, providing a secondary jet having a through-bore that conveys fuel from the main nozzle to the secondary circuit, and locating the filter downstream of the through-bore of the main jet and upstream of the through-bore of the secondary jet. 
 
     
     
       15. The method according to  claim 14 , comprising forming the filter from a plurality of fuel holes that are circumferentially spaced around the main nozzle, and sizing each fuel hole in the plurality of fuel holes small enough to prevent passage of particulate matter that would otherwise restrict fuel from flowing through the secondary circuit.