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Drilling Idle Tubes

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At idle, fuel is drawn through the idle tubes in the carb body. If enlarging the idle feed holes doesn't cure the idle, then Murphy opens up the idle tubes 0.002 inch at a time until the idle is smoother. He uses an extralong drill bit and says you'll see brass falling into the jet cavity as you drill. Murphy warns that you should only drill this by hand, and you must clean the carb very thoroughly after each modification.