I got a chance to run the ST51 this evening after work. I started off with the timing at 20 deg total advance. It idled very good but would only turn 11600 with the same prop it had turned 14100 on glow fuel. Not good. I shut it down and moved the timing to 24 and fired it back up. The rpm's picked up to 12600. I shut it down and moved the timing to 28 and fired it back up. It was now turning 13,300 rpm's. The CHT was running steady at 305F. (Quite a bit hotter than the ST 40) The temp was measured with a fluke meter (I can't remember the exact model but I will look tomorrow) and two thermocouple probes one on the head at the spark plug and the other on the back plate. The back plate at WOT was running 109F. It still idled good but not as smooth as it did with the timing at 20 deg. I then moved the timing to 32 and gained nothing on the top but lost nothing either. The idle was worse and unsteady so I moved it back to 28. That seems to be about as good as I am going get until I have time to move it in smaller increments. I ran two tanks through it (6 oz) and timed the fuel burn on the last. It runs 10 mins on exactly 3 oz at just about 3/4 throttle. It was getting too dark to get any more rpm measurements so I closed up shop for the night. I think it's ready to install in the plane and fly. My plan is to fly it for about 1 1/2 hrs. of run time and then check rod bushings etc. It's looking pretty usable to me. I saw no sign of distress tonight and that was about 35 mins of run time. I will post back when it's flying. [8D][8D]