After reading your first post I was going to suggest looking for a loose wire but I have a feeling you found the answer in the loose pick up.

All engines require tuning after they are purchased. No engine is tuned for best performance out of the box. Believing so will only create a lot of frustration and irritation when the engine fails to perform to the owners satisfaction. You will always have to tune an engine to the enviornmental conditions and the prop selection.

Use a good synthetic oil and use a mix ratio of 70-1 per Gary's recomendations. All Brison engines used to call for a 70 to 80-1 synthetic mix before the company change.

If you have a CH ignition, the minimum battery you should use would be a 4.8 volt, 800 mAh battery. The type does not matter, but the voltage does. An 1,100 mAh, 4.8 volt battery will last you all day.