Hi!

Today when warming up the OS .91 FS Surpass engine just before test-flying my new aerobat the engine suddenly lost revs and quit. It completely lost the compression. The compression was felt through the breather nipple, so the idea was there is something wrong with the valves.

It turned out, that the spring on the exhaust valve collapsed. Valve remained opened all time with gap approx 2 mm wide. I will try to order the spring tomorrow in nearby Graupner shop which sells OS engines and accessories - but the question is how do I replace the spring? Or more specified - how do I dissasemble the valve spring retainer and split cotters?

Engine is Surpass I series (with unpainted metal valve cover) with very low running time - it has burnt around 10l of hi-quality glow fuel (Aerosynth II Competiton). I never had any problems with it.

The luck was that this didn't happened on first take-off or short after.

Sašo