SPECS:

Displacement: 0.545 cu in (8.93cc)
Bore: .906 in (23mm) Stroke: 0.846" (21.5mm) Practical RPM: 2,000-17,000
Power Output: 1.75 ps/16,000 RPM
Weight: 14.25oz (404g)
Recommended Props: 12x7-8, 13x6-7 Crankshaft thread size:1/4-28

Review by: Russ Watson
I have flown the plane several times with the stock " Power Box" muffler and have been very satisfied with the power.  I also went from a 13 x 6 prop to a 12 x 6 prop and the unlimited vertical is even better.  The engine is nearly peaked out on the mixture now that it is well on its way to being broke-in. It has become very fuel efficient.  I could get about 18 minutes of flight on a tank with the .46 AX and I'm getting around 15 minutes at this time with the .55 AX.
 
I originally installed this engine on the the Ultra Stick to break it in until I decided which plane would become its permanent home.  Now that I've seen how it pulls the Stick around, I think I'll leave it forever.