where the throttle linkage connects to the carb the is a screw there, that is lsn. the one oppisite of the idle screw would be a mid range needle. im not 100% that the mach has a 3 needle carb but from what you described that what it sounds like. a pic would help out alot of the needle screws and the idle screw to really be able to help you out. it can be decieving that screw where the linkage connects may look like it is what holds that part onto the carb but it is the lsn.