Thanks to all for the previous help with the motor mount issue.
However now, I have a new problem. After mounting the motor and getting everything tightened down, I noticed/heard/felt a metal grinding. Upon further inspection, this piece was grinding on the motor mount while i was spinning it. I tried readjusting the motor but the two prongs on the end of the piece are just long enough.
Do I need to keep this piece on the motor? Can I take it off? If so, how?
I prolly wouldnt remove the snap ring unless you want the can to fly off at 30mph 
. I would suggest you drill out the motor mount a couple of MM to accommodate the snap ring.
That is a retainer for your rotor, you have to keep it there. Unless you want to experiment with removing it and pretty much replacing it with a pulley. Meaning that you push the pulley towards the motor and lock it with grub screw and that way you could replace it. I have not seen anyone do it but it might just work.
@manners idea is better tho. I would rather sacrifice motor mount that is not that expensive and keep my motor unmodified.
Ok.
Time to bust out the drill!
I have also seen many people recommend using an oversized washer (sits between motor and mount, middle hole big enough to allow for that snap ring space to spin) to give you that 1mm space between the mount and the motor, giving the snap ring/retainer enough space to spin freely.
Or can drill out the mount!
No, you need a washer per mounting bolt, not one in the centre.
The best thing to do is only drill out the mount on the side that the motor sits flush on, just deep enough in to the mount that it clears the cir-clip. Don’t go all the way through if you can avoid it!
The alternative is to file down those prongs on the clip until it clears any snag…
In order of personal preference.
Washers. Washers.
Let it grind untill the retainer finds the place to be, no need it to drill it!!! Jokes aside, I would suggest to make a bit bigger the hole for the shaft. 
Put two small washers between each of the screws that held the motor and the motor mount. One was not enough to clear.
That looks like a 10mm motor shaft. I use 10mm shaft motors on my rigs and when using TB motor mounts, the center hole has to be enlarged to accommodate shafts larger than 8mm. It’s very easy with a Dremel or a flat and round file with some elbow grease.
