Air brake SI DELL'ORTO 120 for SI 20.15-17 AD/20.20 for SI 20.15-17 AD/20.20-26.26E/H/27.23 The main air jet fix on the SI carburettor is located above in the jet block above the main jet and the calibrator. It determines the premix ratio of the gasoline to the air and enriches the gasoline in the jet block with oxygen. It mainly effects the low and medium rpm range, i.e. in the area of ​​1/4 to 3/4 throttle open. If the displacement is enlarged the main jet correction plane should be adjusted. In most cases it also needs to be expanded. Dell'Orto main correction air jets are available for the SI D/H/E and SI G carburetor. As they increase in number (this indicates the size of the hole for the air), the main increasingly lean correction. Conclusion: A must for perfect carburetor tuning in the lower to mediocre rev range. SIP-TIP: Experiment with the mixter tube and different main jets as well. SIP community user 'hofmeisterud' from no 58270000: "Very good quality" ATTENTION: Please take note that we use DELLORTO jets exclusively. It makes no sense to save a few cents and use copy-jet cat. Those who have already tuned carburetors and have found the actual jet diameter does not match the number engraved on the side, what are we talking about. If 105 is on it, then there'd be better than 105 in it! Everything else is a cheap trick.###B05827B120 (MALOSSI)