I can't adjust the carburetor on my 1981. It runs very rich, smokes, and smells terrible! I tighten the idle screw all the way but the engine does not stop. I realized that fuel enters the engine and the idle system is bypassed. I installed a new carburetor but the situation did not change. Therefore, I think that the problem is in the vacuum lines, or some parts of the vacuum system. I would be very grateful if anyone could help me determine what exactly could be causing this. I can't ride it because of this terrible stench!