THE CENTRAL USA ROTAX® independent Service Centre
independent Service Centre FOR ROTAX® AIRCRAFT ENGINES
Bing Carburetor Technical Information
Adjusting the Bing Carburetor
The Bing Carburetor (36mm) is a three stage system: Idle, Midrange, and Top End System. From the moment the engine is started to approximately 1/4 throttle, the carburetor is running according to how the ldle System is set up. As the idler jet number decreases, the mixture gets leaner; (see part# 4), as the number increases, the mixture gets richer. For instance, ldler Jet #45 has a leaner mixture than ldler Jet #50.
The Air Regulating Screw (see part# 10) must be set as stated in the Bing Jet Chart in order to insure smooth operation of the ldler Jet. This screw adjusts the air/fuel mixture at idle speeds and for smooth acceleration. Turning this screw in a clockwise direction creates a richer mixture while turning it counterclockwise creates a leaner mixture. To adjust this screw, gently turn in a clockwise direction until the screw bottoms out, then loosen the screw (in a counter-clockwise direction) the number of turns as recommended in the Bing Jet Chart. For example, the ROTAX 503A would be .5 (1/2 turn) out (effective range 1/2 to 2-1/2 turns out).
Use the carburetor piston Adjusting Screw (see part# 11) to adjust the idle RPM. Turn this screw in a counter-clockwise direction until the Carburetor Piston (see part# 3) is in the lowest position. Then carefully turn the screw clockwise until it just engages the piston and then continue to turn it clockwise for2 to 2-1/2 full turns. This determines the idle RPM of the engine and should be set at 2,000 RPM.
The Midrange System affects the carburetor for approximately 1/4 to 3/4 throttle. Once again, the lower the number of the Needle Jet, the leaner the mixture.
||Needle Jets, Jet Needles
(NOTE: Jet needle must always be under plastic spring cup)
The Jet Needle (see part# 2) has three grooves which the Holding Plate (see part# 3) can be snapped onto. The three grooves are numbered 1. 2, and 3 with number 1 in the top position (note: some jet needles have 4 grooves as in diagram #1 at right). When the Holding Plate (see part# 3); is snapped onto the top position (#1) of the jet needle, a leaner mixture is created than if it were mounted in the #2 groove.
- lnstall sieve sleeve by slightly squeezing it by pushing it all the way up the mixing tube.
- Smaller numbers indicate decreasing jet opening and leaner conditions.
- The #54 marked on the side of the carb is just a casting mark.
- Float guide pins should be polished to insure smooth float action.
- Floats with aluminum guides should be replaced.
- lnspect jet needle grooves for wear every 50 hours.
- Float arm should start out parallel to the float chamber base.
- Fuel pump must be in system to insure correct fuel level.
||How to Check the Float Level
Fuel level below 1/2" will cause a lean mixture.
- Start and warm up engine.
- Run the engine at 3/4 power for 2 minutes.
- Let engine idle back and cool down for 1 minute.
- Shut off engine and fuel system (if the fuel system is an overhead system).
- Remove float bowl.
- Remove the floats from the float bowl while float bowl is sitting on a level surface.
- The fuel level should measure approximately 1/2" from the top edge of the floatbowl.
Fuel level above 1/2" will cause a rich mixture.
Call for Prices on ROTAX Parts