The idler jets on the Bing carb are replaceable. It is recommended that they be replaced if they are found to be plugged. this can happen when the carb is left with fuel in it for long periods of time. The fuel turns to sludge which plugs the jet. In this situation it is NOT recommended that the jet be cleaned and reused. Idler jets start at #30 and increase in increments of 5 to #70 Note on the 582 and 503 DUAL carb Rotax engines we have found that a decrease in the idler jet size provides a smoother engine idle.