...and here's the aforementioned video. I need to do a little more work on processing the data to extrapolate power, but some initial calculations show about 5hp to the wheel, maybe 2.5ft-lb torque while the clutch is slipping (there's about 20% less air here than at sea level, so maybe around 6hp corrected).
That's lower than it should be for this engine, but this was with the wrong-length spark plug, and what felt too rich (but probably just crappy ignition). I think for future runs, I'll use the same stretch of road, it's about as flat as it gets here, a little uphill, but probably less than 1% grade. I'll try and do it when there isn't wind, but with the current gearing those factors are minimal. Hopefully another couple runs today, which I'll film for comparison data after the plug and after (hopefully) getting the jetting dialed in.
I'm using some PHBG clone at the moment, and it's not the best ever, but I've got a real one on the way from Treats with a few needles and a smaller atomiser (going to start by copying the stock KTM jetting, adjusted for altitude, and go from there).