I have a Zenith Pumper carburetor on my pan. It supposedly has adjustable main jet, but even with adjustment at leanest ( CW to bottom) bike still runs so rich as to blacken and foul spark plugs. I cannot find any markings on mainjet body, so do not know what size it is, nor how to find smaller diameter jet for this unit. Does anyone know how to select/ where to get jets. I believe these carbs were used on Pan shovels, and my bike originally had Linkert M74.