Does anyone know where I can get a new 100:1 motor for this from, one of mine spontaneously stopped working. I'm fairly certain no errors were made on my end, so perhaps it was a faulty part? Searching google for the model number on the side hasn't got me anywhere.
If you go onto aliexpress.com and search for "encoder motor 12V 100 rpm" it seems you can pick them up for 5 or so dollars.
I recommend the micro gearhead motors and encoders from Pololu, they are good quality and the ones that were used in the design of the kit. You can burn them up if not careful, like the time I added too many zeros in my PID gains and the wild oscillations made them burn up a few seconds into a test. So just be careful with your control gains and be ready to pull the battery if they sound like they are going crazy.
I'm having the same problem. My micro gear motor is working, but one of the outputs of the encoder seems to be broken (outputs a constant 1.75 volts). I don't know how to fix that so I need a new motor. This is the closest to the motor in the kit (based on the specs provided in the kit) that I've found so far:
But you also have to buy the encoder separately and solder it:
There's also this but the specs don't seem the same:
That looks like you found the right hardware. They are magnetic encoders and the 12 counts per revolution on both of those look good.