ORIGINAL: UStik
This is the successor of the Gold Head, the 60-FSR brought out 1974 (first Schnuerle OS 60). Weight is 470 g / 16.6 oz w/o muffler and 590 g / 20.8 oz with. Power as specified 1.7 hp (maybe without muffler) but realistic (with muffler) is 1.27 hp at 13800 rpm. It may be propped to lower rpm giving good torque.
An interesting point is a hint in the original instruction leaflet: If no muffler pressure is used one should use a carburetor inlet (smaller diameter, more suction) for the 7B carb or use a Perry carb. Might explain the big carb opening?
There was a blackhead model in between the goldhead and the OS .60F SR schneurle ported engine. It was very similar to the goldhead.
My first OS was a .15, but my second OS, the one that I learned to fly "multi" with, was an OS Max .58 R/C. I have managed to collect several of them over the years. The .58 was built in the .50 crankcase version of this engine. Dual ball bearings, a baffled piston and a single piston ring, IIRC. A great running and throttling engine that was equipped with an easy to adjust air bleed carb. Only problem with it was that I couldn't keep the engine running during an outside loop. It could have been a fuel tank problem. I was new in the hobby (1969).
Ed Cregger