Adjusting the Bing Carburetor
The Bing Carburetor (36mm) is a three stage
3.Top End System.
From the moment the
engine is started to approximately 1/4 throttle, the carburetor is
running according to how the Idle 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, idler
Jet #45 has a leaner mixture than idler Jet #50.
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.
screw in a clockwise direction creates a richer mixture
while turning it counter clockwise 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
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.
grooves are numbered 1. 2, and 3 with number 1 in the top
position (note: news 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
- The #54 marked on the side of the carb is just a
- Float guide pins should be polished to insure smooth
- 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
- Fuel pump must be in system to insure correct fuel
How to Check the Float Level
- 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 below 1/2" will cause a lean mixture.
Fuel level above 1/2" will cause a rich mixture.