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Thread: Rotax 503 Exhaust Dimensions

  1. #1
    Less than 10 posts so far! USER IS NOT AVAILABLE
    Join Date
    Jan 2006

    Default Rotax 503 Exhaust Dimensions

    Thought some of you may find this of use

  2. #2
    Less than 10 posts so far! USER IS NOT AVAILABLE
    Join Date
    Feb 2006

    Default Re: Rotax 503 Exhaust Dimensions

    here is loads more info


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    SUN-N-FUN 2007


    APRIL 17th 23rd,



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    JULY 23-29th, HANGAR D, BOOTHS 4041-4042


    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. 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

    Bing Main Jet Needle Coding

    Needles with a "High Number Code" produce RICHER mixtures

    above HALF-THROTTLE. Example: 8L2 instead of 6L1.

    Needles with a "High Letter Code" produce RICHER mixtures

    below HALF-THROTTLE. Example:6P2 instead of 6D2.

    The adjacent regions are also affected to a lesser extent.

    Bombardier Rotax has recently published an updated Bing Jet Chart and Main Jet conversion chart. All ultralights and light planes using ROTAX engines may want to verify what is in their carburetors versus the current recommendations. These new recommendations are a result of continued research and testing which allow the ROTAX engine to perform more efficiently and reliably throughout its power band.

    The Bing Jet Chart Common Application chart shows each engine and the stock carburetion setting at sea level. If you live other than at sea level or in a hotter climate, then you must refer to the Main Jet Conversion Chart to calibrate for altitude and temperature. Air density decreases with decreasing pressure and increasing temperature. If an engine is operated at higher elevation, the weight of the aspirated air decreases, whereas the aspirated fuel quantity remains practically the some. This results in richer fuel/air mixture than at lower sea level.

    If the engine is operated in high altitude for a longer period, it is necessary to adjust the carburetor calibration to re-establish the original composition of the fuel/air mixture. With increasing altitude (lower air pressure), the oxygen quantity sucked in by the engine decreases. The consequent loss in performance cannot be compensated for by different carburetor settings.

    To adjust the carburetor, in general a different main jet size is sufficient. Only in very particular cases a different needle jet and/or different idle jet also has to be installed.

    EXAMPLE: If a ROTAX 503 engine set up for sea level is shipped to Colorado Springs, Colorado, (approximate elevation 6,500 feet), the main jet would have to be changed. Our Bing Jet Chart shows the ROTAX 503 SCA (single carb, with a K & N Air Cleaner and without an intake silencer or after muffler) would have a main jet of 180 for sea level. By using the conversion chart, going to the approximate altitude of 6,500 feet and using the temperature of 50 degrees fahrenheit, you can see we have a multiplier of .95 and come up with our recommended jet of 171. This main jet will produce the same composition of air/fuel mixture that the 180 main jet would at sea level. Temp

    °F Temp

    °C Altitude (meters)

    0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000

    Altitude (feet)

    0 1,640 3,281 4,921 6,562 8,202 9,842 11,483 13,123

    -22 -30 1.04 1.03 1.01 1.00 0.98 0.97 0.95 0.94 0.93

    -4 -20 1.03 1.02 1.00 0.99 0.97 0.96 0.95 0.93 0.92

    14 -10 1.02 1.01 0.99 0.98 0.96 0.95 0.94 0.92 0.91

    32 0 1.01 1.00 0.98 0.97 0.95 0.94 0.93 0.91 0.90

    50 10 1.00 0.99 0.97 0.96 0.95 0.93 0.92 0.91 0.89

    59 15 1.00 0.99 0.97 0.96 0.94 0.93 0.92 0.90 0.89

    68 20 1.00 0.98 0.97 0.95 0.94 0.93 0.91 0.90 0.88

    86 30 0.99 0.97 0.96 0.94 0.93 0.92 0.90 0.89 0.88

    104 40 0.98 0.96 0.95 0.94 0.92 0.91 0.90 0.88 0.87

    122 50 0.97 0.95 0.94 0.93 0.92 0.90 0.89 0.88 0.86

    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.

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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 floatbowl.

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

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

    2 Cycle Troubleshooting

    Engine Oil Mixing Chart

    Gas-to-Oil Mixing Instructions, 50:1 Ratio Gas, gal. Oil, oz. Gas, gal. Oil, oz.

    1 2.56 (75.8 cc) 6 15.36 (454.8 cc)

    2 5.12 (151.6 cc) 7 17.92 (530.6 cc)

    3 7.68 (227.4 cc) 8 20.48 (606.4 cc)

    4 10.24 (303.2 cc) 9 23.04 (682.2 cc)

    5 12.80 (379.0 cc) 10 25.60 (758.0 cc)

    Use this table to determine how much oil to add to a given

    quantity of gasoline to make a 50:1 ratio.

    Rotax Engines

    Rotax 377 Engine

    Rotax 277 Engine

    Rotax 447 Engine

    Rotax 503 Engine

    Rotax 503 Dual Engine

    Rotax 582 Engine

    Rotax 618 Engine

    Rotax 912 Engine

    Rotax 912-S Engine

    Rotax 912-F Engine

    Rotax 914 Engine



    For all other technical questions e-mail Leading Edge Air Foils at

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