If your saws been sitting around a while you want to start with fresh gas and a clean air filter. Adjust the idle screw until the saw keeps running without spinning the chain (Should be around 2500 rpm). You probably have limiter caps and a limiting ignition coil on that will keep you from going too low or above 13,500 rpm. Once the saw is warmed up you can tune with the low and then high needles. Its best to use a Tachometer to get the correct rpms. If you cant tune it within the limits you may have another problem.