Recommended Bing Carbs for 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.

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

Rotax Engines with Intake Silencer

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

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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.

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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.

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