Buy with confidence !! The engine is very powerful, very stable, smooth transitions !!
I installed it in an inverza 33 and I have an exceptional set !!
I like to use small propellers, I'm turning an 18x8, the engine turns light and very powerful. Working temperature always below 90oC. I only have complements for this excellent engine!
The engine is so quiet, that sometimes it’s bad to fly with others flying, you don’t hear your engine!
No more DLE or DA for me .
OS gas is better then both .

I have 2 of these mounted in 73” 3D aircraft. For my particular style of flying, these both provide PLENTY of power on the recommended break-in prop.
Vertical is unlimited, pulls outa hovers nicely, and transitions perfectly. Starting is a bit tricky, as these will start AND run backwards. I’m left handed, so I squat on the right side of the aircraft and pull the prop through from underneath. If I don’t pull completely through, she’ll fire n run backwards, which I didn’t think could happen, but it does.
Choke, ign OFF, pull the prop though a couple times, ign ON, she’ll fire on the second flip. Ya gotta flip the prop through all the way!. Choke off, 2-3 flips and she fires right up. A pinch fat on the top end for break-in, and let er rip. This engine is strong, reliable, and responsive. I’m actually amazed at the compression I’m seeing before I have the engine even broke in.
One thing that is puzzling me though, I have “blown out” 2 after market Pitts style muffs. One muffler failed at the apex of the 90° weld, and the other split the muffler can apart from the header flange, like cracking an egg???? If this is a vibration issue, well, I’m gonna find out. I’ll mount the stock single tube Pitts muffler and wring it out. If I have any more failures, I’ll be sure to post that update. I don’t have any reason to believe that the engine or prop are THAT out of balance. But blowing out 2 muffs on the same engine is a bit questionable.

Ran this engine for about 8 times and it stopped in mid flight..I retrieved it and the back plate and mount was broken in 4 places. This part was made so thin that it will hardly stand a bench break-in...made of white metal and fragile..on top of that a new one is just $30.00.
I have always used OS but this one is less than a 5 star---however when it run--like a scalded
dog pulled good and very powerful---they need to beef up the back cover if they have not already done so--