The first time that I encountered a .61SF engine was when I test flew a fellows kit built Super Kaos in 91 or 92. He had a humongous looking prop on it for an 11x7 user like me. I asked him about it and he said that it was the size that the manual recommended. He had bench ran the engine until it was sweet, so no further attention had to be paid to break-in. I had been away from the hobby for a few years and had missed some of the OS long stroke info that had circulated.

The Super Kaos was built beautifully, but had been painted, so it wasn't as light as it could have been had plastic film been used to cover it.

A few laps around the flying field and I had it trimmed out to where it was comfortable to me. It was time to play.

I pulled back on the elevator in order to go straight up for a couple of hundred feet, fully expecting this over propped sixty to fade out, causing me to terminate the climb. Wrong. The model just kept going up and up and up and up with nary a sign of fading out (overheating). I was astounded. This was a stock muffled engine without a pipe/pump/or over sized carb. While it didn't rev up all that high, it didn't slow down when going vertical. That was when I fell in love with the OS .61 SF/RF engines. I now have half a dozen of them.


Ed Cregger