JETS-R-US: CARB SWAPPING CONVERSION
AND
CONVERSION FOR KEIHIN TO MIKUNI TO DYNOJET

Question, I am swapping a Keihin carb for a Mikuni carb, what jet do I use? The table below may give a place to start. For example lets suppose that a Mikuni carburetor has a size 100 main jet in it, the equivalent Keihin jet would be a 110. After the carb swap to a keihin carb start with keihin 110 jet. The chart will not be a perfect match because there are many variables, for example, different carb flow characteristics, different needles, orifices etc. but it is a starting point.

Question, I have some dynojets and would like to purchase Jets R Us jets, how do I compare the sizes? Dynojet does not produce hex jets, only round and therefore dynojet provides a main jet adapter. Because dynojets are not manufactured 100% the same as mikuni and keihin there is not an exact comparison between the two, flow rate may be different.

 

Note that Keihin jets cannot be placed in Mikuni carbs and vice versa.

The table below is an approximation, results in the carburetor will vary, due to fluid dynamics these will not be exact equivalent flow rates.

Diameter Keihin Dynojet Mikuni
.025 70 74 70
.026 72 76  
.027 75 78 72.5
.029 78 80 75
.030 80 82 77.5
.031 82 84  
.032 85 86 80
.033 88 88 82.5
.034 90 90 85
.035 92 92  
.036 95 94 87.5
.037 98 96 90
.038 100 98 92.5
.039 102 100  
.040 105 102 95
.041 108 104 97.5
.042 110 106 100
.043 112 108  
.044 115 110 102.5
.045 118 112 105
.046 120 114 107.5
.047 122 116  
.048 125 118 110
.049 128 120 112.5
.050 130 122 115
.051 132 124  
.052 135 126 117.5
.053 138 128 120
.054 140 130 122.5
.055 142 132  
.056 145 134 125
.057 148 136 127.5
.058 150 138 130
.059 152 140  
.060 155 142 132.5
.061 158 144 135
.062 160 146 137.5
.063 162 148  
.064 165 150 140
.065 168 152 142.5
.066 170 154 145
.067 172 156  
.068 175 158 147.5
.069 178 160 150
.070 180 162 152.5
.071 182 164  
.072 185 166 155
.073 188 168 157.5
.074 190 170 160
.075 192 172  
.076 195 174 162.5
.077 198 176 165
.078 200 178 167.5
.079 202 180  
.080 205 182 170
.081 208 184 172.5
.082 210 186 175
.083 212 188  
.084 215 190 177.5
.085 218 192 180
.086 220 194 182.5
.087 222 196  
.088 225 198 185
.089 228 200 187.5