The title says it all. It fired up on the first three flips of the rotary start on a test stand. Use MorganFuel Omega 15% nitro, more commonly known as the “pink stuff” and on the first fire up, push it to full throttle AFTER setting the high speed needle valve VERY rich, let it run at full throttle for one minute running VERY rich so that it “four cycles” and “spits fuel from the muffler”, then lean the engine to ~500rpm below peak rpm of ~16500-17000 (use an APC 10x7 or 11x6 or 12x5 prop), then richen it after 10 seconds running 500rpm below peak, let it run full throttle very rich for another 10 seconds, and repeat that back and forth procedure until the tank is empty. Do this on the ground obviously. Then for the first 3-5 flights, run it rich. I put this engine with a Macs one piece muffler on a very heavy Hangar 9 Jackal 50 and it gave decent performance. I think for my second Jackal I’m going to use an OS 95, since it has the same bolt pattern as the OS 61. There’s no replacement for displacement they like to say. The break in procedure MUST be followed for maximum performance. A Macs muffler or tuned pipe helps a lot too. I’ve probably had at least three dozen flights on it, and not a single dead stick. That’s reliability. Great engine.