I must be missing something here. My Rotax engine is a year and a half old and it starts instantly every time I start it and I don't think it is a special engine. I have read several comments regarding high and low idle RPM. When I went to the Rotax engine school we were instructed that the carburetors do not have a choke but the do have a starting valve that enriches the mixture for starting only.If the throttle is advanced (high idle speed setting)to far, it takes the starting circuit out of this system. So what this means is if the idle is set around 2000 RPM or more, the starting valve providing a rich mixture cannot function. The idle should should be set around 1600 to 1800 and used only for starting. As soon as the engine starts, the throttle should be advanced to 2400 RPM for a minute then RPM reduced to 2000 RPM (minimum) preferably 2400 RPM until the engine warms up. The pilot or operator should not rely on the idle setting, he should control the idle RPM with the throttle and only use the lower RPM (i.e.1800 RPM) for shutdown. If the idle setting is set to 1600-1800 RPM,with the throttle fully closed, the enrichment circuit will function normally enabling a rich mixture for a quick start just like you had a choke. If the throttle is not fully retarded during starting you will have a hard starting engine every time. When my engine is warm, it starts instantly with the throttle retarded to a notch off full stop.
Dick Russ
RFSC-IRMT 912
A&PIA
