The early WW1 Le Rhone rotary engines had no thottle. They ran at full thottle all the time and you slowed it down by turning off or blipping the mag. Maybe you could install a servo to operate a kill switch and you could blip the mag to help slow it down. I converted a Ryobi and get about 2000 rpm on idle and was wondering if that would be too high for my Senior Telemaster?? It will be ready this spring so I will know then.