For 2 consecutive weekends I have had problems with my Supertigre GS-45 (turning a 10x7 prop) which is installed onto an Avistar trainer. The engine runs well when tested in the floor even when making quick changes in the throttle up and down. However in the last flights I have made I have detected some coughing (or should I say sputtering) that happens when I do small adjustments to the throttle (2-3 clicks up or down) just to fight the wind and after that it continues to run consistently. I must clarify that this coughing doesn't happen all the times I do these small adjustments in the throtle.

Yestarday this coughing happened just when I was making my first turn after the takeoff and it kept sputtering while I was fighting to avoid the plane fm stalling... at the end gravity won and I had to run to the place I saw the plane crashed expecting to see bits and pieces all over... Lucky me it fall into high grass and that absorbed the impact with just a cracked elevator stab...

So, while I am in my way to repair the avistar I keep thinking what is wrong with the engine... I checked the fuel tank and the fuel lines and everything seems to be ok... I am using powermaster fuel but I am not using fuel filter... could it be the engine is clogged with some stuff fm the fuel? Should I clean it? How to?