Actually, to tighten the rotor belt is a misleading description. Adjusting the belt, is more acurate. As you are really not doing much tightening, you're adjusting the distance between the two pulleys so that the variable speed has proper range of adjustability. The belt is actually tightened when power is applied to it. That adjustment should not make any problem going into low gear. If the linkage pin is hitting something, then it must be bent slightly. If you have it all straight, and no obstructions are in the linkage path, then you need to do more tests to find the problem. Next time you service the machine, run the seperater for maybe 30 seconds or so, shut the engine off, and pull the rotor gearbox oil dipstick and wipe the oil off on a white paper towel and look for any silver sparklely matter in the oil. If it has metal slivers and pieces in it, I would'nt want to be in your shoes. Just curious, why were you adjusting the rotor beltIJ Was it slippingIJ Or did you put a new one onIJ