Saw was purchased in 2000, has what I gather to be the older style of plastic caps that have the wings on them. I clipped them off without removing them to allow turning the H and L screws. Problem is, they just rotate around but the actual screws do not move. How do I remove these so I can get the carb adjusted properly? It is running way over max rpm and I don't want to damage the engine by allowing this to continue. Any suggestions appreciated!