The small os engine ran quite smoothly and was slightly quieter than a comparable .40. I ran mine without the muffler and was not noticably louder then my ASP .40 with muffler. Very low vibration. VERY thirsty......approx same power output as a .40 but drank like a .60. Also, VERY hot exhaust, similar to a 4 cycle glow engine. I used a smoke system on mine and just pumped the smoke oil into a short exhaust header.....worked just fine. I purchased that engine in the late '80s and retail at that time was under $225. They have gone up in price dramatically.

At the same time I owned a 1987 Mazda RX-7 turbo....also very smooth and high-reving but only got about 13mpg.

The large graupner engine was available only for a very short time...was rather expensive, and produced about 5hp.

PT