Haien said:
The battery will be 22s and 20Ah, weighing right around 10kg. With a comfortable back pack that will be no problem.
Time for a math check. For 16kW @ 82V nominal (22S), you need ~200A continuous. Using high current 18650 cells, e.g. Samsung 25R, 2500Ah, you need 8P. 25Rs can provide 20A when new and under ideal conditions. 8P of 25Rs can provide 160A. For 200A, you'd need 10P (220 cells), or 22lbs of cells. So 22S10P, 25Ah, 200A, or 7.5 minutes of riding at 16kW.
If you go lipo, then using 6S 20Ah and 4S 20Ah in combination 3x6S, 1x4S for 22S, then that comes to 21.6 lbs, using Turnigy lipo packs. At 12C, that would provide 240A when new, and under ideal conditions. I would worry about crashing with 22lbs of lipos strapped to my back. Do you have experience with big lipos? They're economical, but dangerous, and I'd probably go for something like 25Ah+ worth for 20Ah of usable capacity, or 6 minutes of riding at 16kW, or 7.5 minutes if you run them down.
Since you're looking for 16kW peak, you don't need as big or heavy a motor for that, just a battery to support it. I've hit 7kW peak into my cheap 1000W ebay hub, but 4kW (peak) regularly. I'm guessing the Leafbike motor suggested earlier may take 12kW for very short bursts; there's probably experience members that could speak to that though.
I have some familiarity with high power motorcycles. I have one that will power wheelie in the first 3 gears just by rolling on the throttle (no revving or clutch). The ascending torque curve of a motorcycle engine is way easier to control than the descending torque curve of an electric motor. Rolling on the throttle on a high power electric bike, is like running your motorcycle up to 6000 rpm into the meat of the torque curve, and dumping the clutch. So you have a lot of unusable torque for the first 15 mph or so.