Gday
Hopefully somebody can help me out. I am running a YS 63FZ on 20/20 fuel (CoolPower) however seem to be running into a few problems. On take off the engine is excellent, plenty of power and no sign of any problems. However, flying around, I pull vertical and this is where the problems start.

On pulling vertical, the engine coughs, just seems to load up. It seems to start to labour, and then stops.

I am running an APC 13x6 prop and it is pulling 11,400rpm or so.

Please excuse my ignorance in asking this question, however I am new to the use of the YS engines, and so far I like what I have experienced, however would just like to sort this problem out.

Regards
Chris