OS AX .46 Kicks/Whacks at idle

by Ruben Mifsud
(Malta)

I have have an OS .46AX having quite some running hours. On medium and high speed the engine runs smoothly (smooth rpm), but on idle it is sort of kicking/whacks.

I also notice that from the exhaust significant unburned fuel/oil emerge and after a few seconds of idle, such like as you taxi out your plane from the pit to take of, if I open the throttle quickly to full it coughs and stop.

I have to open the throttle slowly to half open to clear before I can open fully to the second half. In flight throttle response shows no problems.

They seem to be all signs of a rich mixture, but if I close the high speed needle further the does not keep it's high rpm steadily when I point the model skywards. I am puzzled. Thanks