Recommended Bing Carbs for 2 Stroke Rotax Engines

These carbs come with recommended jetting from the bing jet chart.
All these Bing carbs come with a hand lever choke. Except where
noted these Bing carbs do not come with a silencer.

 BING 1           Image result for rotax 912 carb

Engine

Part #

Description

277 A

995-570

Bing 36 mm

377 SCA

995-514

Bing 36 mm

377 DCA

292-355

Bing 32 mm

447 SCA

887-810

Bing 36 mm

447 DCA

292-357

Bing 32 mm

503 SCA

995-510

Bing 36 mm

503 SCB

995-512

Bing 36 mm with Rotax air intake silencer

503 SCA

996-413

Bing 36 mm

503 SCB

996-414

Bing 36 mm

503 DCA

886-085

Bing 36 mm

532 SCA

995-865

Bing 36 mm for SMX only

532 DCA

995-864

Bing 36 mm

582 DCA

995-864

Bing 36 mm

618 DCA

886-087

Bing 36 mm

 

Recommended Jetting for Bing Carburetors

The following is the factory recommended jet for Bing carburetors at sea level 

and 70F degrees. Apply the Bing Main Jet Correction Chart shown at the 

bottom of the page to compensate for temperature

 and altitude at your location. Jetting for engines equipped 

with intake silencers are also listed.

Rotax Engines w/o Intake Silencer

Engine Type Main
Jet
Idler
Jet
Needle
Jet
Jet
Needle

Clip from top

Air
Screw

Rotax 277 148 45 2.72 8L2 2 1.0
Rotax 377 165 45 2.70 8O2 2 0.5
Rotax 447 165 45 2.70 15K2 2 0.5
Rotax 447 DC 135 50 2.70 6G1 3 1.0
Rotax 503 SC
Up to Serial #3785371
180 45 2.74 8G2 3 0.5
Rotax 503 SC
After Serial #3785372
185 45 2.72 15K2 3 0.5
Rotax 503 DC 158 45 2.70 11K2 2 0.5
Rotax 532 SC 195 55 2.74 15K2 3 1.0
Rotax 532/582 DC 165 55 2.72 11G2 3 1.0
Rotax 618 DC 158 55 2.72 15E5U 3 1.0

Rotax Engines with Intake Silencer

Engine Type Main Jet Idler Jet Needle
Jet
Jet
Needle
Clip Airscrew
Rotax 277 140 45 2.72 8L2 2 1.0
Rotax 377 155 45 2.70 8O2 2 0.5
Rotax 447 155 45 2.70 15K2 2 0.5
Rotax 447 DC 128 50 2.68 15K2 2 1.0
Rotax 503 SC
UP to Serial #3785371
158 45 2.74 6H2 3 0.5
Rotax 503 SC
After Serial #3785372
165 45 2.70 15K2 3 0.5
Rotax 503 DC 148 45 2.68 11K2 2 1.0
Rotax 532 SC 170 55 2.74 15K2 3 1.0
Rotax 532/582 DC 145 55 2.68 15K2 3 1.0
Rotax 618 DC 135 55 2.70 15E5U 3 1.0


Bing Correction Chart

How to Use the Bing Main Jet Correction Chart

Step #1 - Disassemble and check your carburetor(s) to verify the recommended

 jetting listed in the recommended Bing jetting chart is installed in your Carb(s). 

This is the most up to date information available at the time of this publication.

Step #2 - Because air density varies with temperature and altitude changes, 

a main jet correction may be necessary. This chart was calculated at sea level 

with an air temperature of 60F or 15C.

Step #3 - Apply the multiplication factor shown to the main jet size 

recommended in the chart at the top of the page.

Step #4 - Your operating conditions will vary by the change of seasons. 

If your EGT  temps vary and your engine experiences performance difficulties,

 a review of your jetting may be necessary. Return to step #2.

Step #5 - Humidity is also a variable in determining air density. 

A high humidity means a lower air density of air to be consumed by combustion. 

Because we are generally not equipped with a way of easily reading the % of humidity present,

 this can be read in to this chart by adding altitude on high humidity days and 

subtracting altitude on in very dry climates. An EGT gauge should illustrate changes

 in these conditions under lull throttle readings.

Main Jet Correction Chart ................ 
Example: 160 x 0.89= 142 Main Jet

Altitude - Meters 0m 500m 1000 1500 2000 2500 3000 3500 4000
- Feet 0' 1500' 3000' 4500' 6000' 7500' 9000' 10500' 12000'
Temperature                  
-22F -30C 1.04 1.03 1.01 1.00 0.98 0.97 0.95 0.94 0.93
-4F -20C 1.03 1.02 1.00 0.99 0.97 0.96 0.95 0.93 0.92
14F -10C 1.02 1.01 0.99 0.98 0.96 0.95 0.94 0.92 0.91
32F 0C 1.01 1.00 0.98 0.97 0.95 0.94 0.93 0.91 0.90
50F 10C 1.00 0.99 0.97 0.96 0.95 0.93 0.91 0.90 0.88
59F 15C 1.00 0.99 0.97 0.96 0.94 0.93 0.92 0.90 0.88
68F 20C 1.00 0.98 0.97 0.95 0.94 0.93 0.91 0.90 0.88
86F 30C 0.99 0.97 0.96 0.94 0.93 0.92 0.90 0.89 0.88
104F 40C 0.98 0.96 0.95 0.94 0.92 0.91 0.90 0.88 0.87
123F 50C 0.97 0.96 0.94 0.93 0.92 0.90 0.89 0.88 0.86
 

 

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.
ldler Jets
     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.
  1. lnstall sieve sleeve by slightly squeezing it by pushing it all the way up the mixing tube.
  2. Smaller numbers indicate decreasing jet opening and leaner conditions.
  3. The #54 marked on the side of the carb is just a casting mark.
  4. Float guide pins should be polished to insure smooth float action.
  5. Floats with aluminum guides should be replaced.
  6. lnspect jet needle grooves for wear every 50 hours.
  7. Float arm should start out parallel to the float chamber base.
  8. Fuel pump must be in system to insure correct fuel level.

How to Check the Float Level
  1. Start and warm up engine.
  2. Run the engine at 3/4 power for 2 minutes.
  3. Let engine idle back and cool down for 1 minute.
  4. Shut off engine and fuel system (if the fuel system is an overhead system).
  5. Remove float bowl.
  6. Remove the floats from the float bowl while float bowl is sitting on a level surface.
  7. The fuel level should measure approximately 1/2" from the top edge of the float bowl.

Fuel level below 1/2" will cause a lean mixture.
Fuel level above 1/2" will cause a rich mixture.

Print this page