Carburettor needle for PHVA/PHBN carburettors The throttle needle, together with the mixing tube, regulates the composition of the mixture in the part-load or half-throttle range. Needles vary in diameter, length & pitch, with each of these aspects having a specific influence on the mixture composition. Generally speaking, a thicker needle results in a leaner mixture. A longer needle causes the mixture to be richer. The needle also has four clip positions that can be used to adjust its position. The higher the clip is positioned on the needle, the deeper the needle dips into the mixing tube, resulting in a leaner mixture in the half-throttle range. If the needle is already in the lowest position & the mixture is still too rich (recognisable, for example, by the four-stroke with the slide half open), you should consider a thicker needle or a smaller mixing tube. OEM numbers (for comparison purposes): B16250.013 (MALOSSI) 1625013 08 (DELLORTO) Article: Dell Orto DELLORTO Conical...