The Ryobi is a wet sump eninge and will run inverted but isn't as happy as right side up. Also, if you store it inverted, it tends to leak oil past the rings and out the case vent, screwing up the combustion chamber and your floor. Once running, doing loops and flying inverted is fine but I lost nearly 1000 rpm static with it inverted.

Volfy is right, they aren't power-houses but are fun, quiet, clean, and super economical. I can burn about 12 per hour of putting around.

From reading other threads, it sounds like the Honda GX25 and the Stihl 4-mix will be more powerful. I also haven't seen any numbers on the Shindaiwa engine.

Doug