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Rotax Aircraft Engine Bing Carburetors

These informations and much more can be found in our Engine Maintenance Logs.

Rotax 2-stroke Aircraft Engine Bing Carburetor Configurations

 
Carburetors
Intake Silencer
Main Jet
Idle Jet
Needle Jet
Jet Needle
Needle Clip
Air Screw Turns
Rotax 277 UL 1 No 148 45 2.72 8L2 2 1
1 Yes 140 45 2.72 8L2 1 1
Rotax 377 UL 1 No 165 45 2.70 8O2 2 ½
1 Yes 155 45 2.70 8O2 2 ½
Rotax 447 UL 1 No 165 45 2.70 15K2 2 ½
1 Yes 155 45 2.70 15K2 2 ½
2 No 135 50 2.70 6G1 3 1
2 Yes 128 50 2.68 15K2 2 1
Rotax 503 UL
up to #3785371		 1 No 180 45 2.74 8G2 3 ½
1 Yes 158 45 2.74 6H2 3 ½
Rotax 503 UL
after #3785372		 1 No 185 45 2.72 15K2 3 ½
1 Yes 165 45 2.70 15K2 3 ½
2 No 158 45 2.70 11K2 2 ½
2 Yes 148 45 2.68 11K2 2 1
Rotax 532 UL
582 UL		 2 No 165 55 2.72 11G2 3 1
2 Yes 145 55 2.68 15K2 2 ½
Rotax 618 UL 2 No 160 PTO
170 MAG		 50 2.68 9M10J 2 1
2 Yes 135 PTO
145 MAG		 50 2.68 9M10J 2 1½

Adjusting Rotax 2-stroke Aircraft Engine Bing Carburetors to atmospheric conditions

The fuel/air mixture the carburetor provides to the engine varies with air density. Air density fluctuates with ambient temperature and altitude above sea level.

It is sometimes possible to adjust the mixture by changing the position of the needle clip, but for great variations in atmospheric conditions, a change of main jet is necessary.

The formula for finding the required main jet is the following:

J2 = (D2 / D1) X J1

D1 = Original density factor
D2 = New density factor
J1 = Original main jet
J2 = New main jet

Refer to the chart below to find density factors.

  m 0 500 1000 1500 2000 2500 3000 3500 4000
°C °F/ft 0 1600 3300 5000 6500 8200 10000 11500 13000
-30 -22 104 103 101 100 98 97 95 94 93
-20 -4 103 102 100 99 97 96 95 93 92
-10 14 102 101 99 98 96 95 94 92 91
0 32 101 100 98 97 95 94 93 91 90
10 50 100 99 97 96 95 93 92 91 89
15 59 100 99 97 96 94 93 92 90 89
20 68 100 98 97 95 94 93 91 90 88
30 86 99 97 96 94 93 92 90 89 88
40 104 98 96 95 94 92 91 90 88 87
50 122 97 96 94 93 92 90 89 88 86


For example: your mixture was perfectly adjusted with a 158 main jet to fly at sea level and a temperature of 20ºC, but you decide to use your engine in a region at 1500m above sea level and a temperature of 30ºC. What main jet will you need?
J2 = (94 / 100) x 158 = 0.94 x 158 = 148.52
The result is rounded to the next available larger main jet, in this case 150.

Rotax 4-stroke Aircraft Engine Bing Carburetor Configurations

 
Main Jet
Idle Jet
Needle Jet
Diffuser
Jet Needle
Needle Clip
Air Screw Surns
Rotax 912 UL 158 35 2.72 961200 961215 3 1½
Rotax 912 ULS 155 35 2.70 961202 961215 3 1½
Rotax 914 UL cyl. 1/3 160 35 2.72 961200 961215 1 1½
cyl.2/4 164 35 2.72 961200 961215 2 1½