For trainer engines (also for 2nd plane use): 1. OS 46AX, pricy but easy to start and tune and tons of power if you can afford it at all, you won't be sorry! The user friendliness, reliability and extra power when it gets windy will be appreciated on the first flight.

2. Thunder Tiger 46Pro, a less expensive but still very good alternative. As an instructor I found them also to be as easy to start and tune as the OS but not quite the same power, but close enough. Any other brand in this size just doesn't give the reliability needed for nice training flights IMHO. [8D]