Swapping the mid-drive assembly is a very straightforward process and typically takes less than an hour. Please read these instructions all the way through before beginning.
DISCONNECT AND REMOVE THE BATTERY FROM THE BIKE! This will guarantee that there are no accidental short circuits.
1) Remove dust cap and nut (or bolt in some cases) from the left side crank arm.
2) Using a crank puller, remove the left crank arm.
3) Remove the black plastic disc -- it just slides off. (Circled below)
4) Using a Phillips screwdriver, remove the PAS sensor as shown below. IMPORTANT! Set aside this screw and do not lose it. You can just let the sensor hang freely.
5) Pull the motor wire connections free of the frame and unplug them. The 3 thicker wires may have shrink wrap on them-- just use scissors or diagonal cutters to cut the wrap off:
6) Once the motor wires are free, remove the two nuts on the main mounting bolts. You will need to hold the bolt head with a wrench from the right-hand side of the bike:
7) Once this is complete, you can remove the bolts. IMPORTANT: If they seem stuck, you may need to drive them through, but you must use a punch tool to do this! Hitting the bolts directly will only damage the threads, and they won't come clear of the frame anyway. IMPORTANT: Support the Mid-Drive Assembly as the second bolt is removed, as it is quite heavy and will be 100% free of the bike once the bolt comes out.
Installation is the reverse of removal, with the following considerations:
1) Inserting the bolts through the frame can be a little tricky, as the chainring may need to be rotated to pass the punch through to drive the bolts. See below:
2) When reconnecting the motor wires, the best method to cover the contacts of the 3 individual thick wires is to use shrink wrap and a heat gun. 5/32" x 1 3/8" tubes work very well ( a heat gun works best-- you may have luck with careful use of the flame from a lighter). Alternatively, you can wrap the connections with electrical tape, but be thorough and generous-- you want to prevent these connections from touching each other or the frame.
3) The two bolts need to be VERY tight-- if you have a torque wrench, tighten to 30 ft/ lbs.
4) You will need to transfer the pedals-- keep in mind that the right pedal screws ON Clockwise, but the Left side is reverse threaded and tightens COUNTER-CLOCK Wise.