I have run a ST 2300 in the past and am currently running an O.S. 1.60. I have not used a pump on either or these engines. I did make some mods to the ST carb to solve the mid-range problems. In both of my engines I am running medium size fuel line. On the ST I ran the stock muffler, but did plug one of the outlets. On the O.S. I am running a Bisson pitts muffler and also plugged one of the outlets. On both engines mixture has been consistent throughout the flight. I am also using O.S. "F" glow plugs in both engines. Both engines are excellent in aerobatics. The ST was in an old style Ultra Stick. The O.S. is currently in a 1/4 scale Aeroworks Edge 540. Both have unlimited vertical. Both engines have been very reliable and more than adequate for the task!

I hope you find some of this interesting.

Steve