From the start the Stratus was going to have an electric assist installed. I'm in my fifth year without a car, in a rural area, in the middle of a transportation system that was 99.9% designed for cars. The electric assist helps me compensate for the poor road design, the distances, and the nonexistent bus and train network. Also, recumbents aren't as easy to peddle uphill, and there are plenty of hills here. So I took most of the original drivetrain parts and stored them in a plastic zip bag in case the bike needs to be restored later on.
Because they can be shifted to different gearing ratios, I've found Bottom Bracket motors are more versatile than the hub motors I've used. I knew the Stratus was going to be fast, but it also had to climb up my dirt road. Because my state recently enacted the (questionable) 3 class ebike legislation and I wanted to stick with 750 Watts, I decided to use a Bafang BBS02. It's more powerful than the 500 Watt Tongsheng TSDZ2, and not as heavy as the Bafang BBSHD,
I'd installed a dozen BBS02 which had been strong and reliable motors, but then the 13th motor had a manufacturing defect:
The sensors themselves could have been bad, so I tested them before reassembling the motor. With a voltmeter connected between the ground and the output of each sensor, the output should toggle between a high and a low voltage when a magnet (a magnetic screw holder in this picture) is passed by the sensor. If you are trouble shooting this part and not familiar with doing this, please unplug the Hall board from the circuit and use a separate power supply. Note: these appear to be latching Hall sensors, and the magnet has to be flipped to the other side to change the polarity. I had expected the vendor to send a replacement Hall sensor board so that it could be swapped easily, but they cheaped out and sent one single Hall sensor. I don't think this would have helped most bicycle shops.
This 14th motor has been working fine, it's smooth, quiet, and pulls nicely. I reprogram the BBS02 motors mainly to turn the power down in the first and second assist levels for easy riding. With these settings, the bikes ride a lot like the Specialized Turbo Como in our ebike library. I also change a few other settings, such as reducing the starting current to prevent a large starting load from burning out the motor, but I don't do anything complicated. There is a ton of BBS02 programming information available on the web so I'm not going to repeat it here. (I use Penoff, Endless Sphere, EM3EV, Karl Gesslein, Lectric Cycles, and Lunacycle suggestions.)