Had one once, once being the key word. Seriously, they need 5% fuel and a good carb will do wonders. I sent mine back to Horrizon as no one could make it reliable after three carbs..
Use a carb such as a Super tigre or MVVS, If the base is slightly oversize or of the proper size it will do wonders. The oversize base can be turned down to fit your engine.
Mine had serious power just quit on most flights, finally got the high end and low end right, the mid-range loaded up.....all carb.
Good luck