Hi, I have a HT 131 Pole Saw, The manual says it should max out at 10,500 RPM, I checked it with my Tach and it is only getting to about 9,800 sometimes ten, If I hold it long enough it starts to cut out or break up like there is a rev limiter on it or something. I tried turning the H Speed screw and nothing happens Rpm's barley Change if at all. I can only turn them less then a full turn.