I use a similar motor but size is 6364 which obviously would have more material than say 5055. Like in photo mine has also taken a beating and still no issues.
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Iām in NYC. That really cool of you. I would gladly send it to you and test yours in my setup. yes you can use my video and pictures.
I wonder if your motor mount is bent or that mount point is somehow off plane with the rest of the mount points. The fact that the failure is exactly the same both times and no one else (that I know of) has had this issue leads me to be suspicious that something is going on here not related to the motor?
I could see where a constant upward pressure on that part of the motor would eventually cause the metal to fatigue and separate.
Everything is aligned i check meticulously before every ride. I have had issues with this before and iām very aware of it now. I assure everyone my mount is aligned and the pulleys are centered. I was thinking the belt might be a little tight. But the motor spins freely and isnāt held back by the tightness.
Every time I think it could be my fault i remember that this problem happens twice in the same exact spot and nothing like this every happened to my sk3. This happened probably for the same reasons my mounts cracked also. The manufacture puts too many holes in the metal it will not hold.
Bottom line is beware of thin metal and too many holes in anything you use.
Just a side note. Also check what @chaka had to say about running 63mm motors on any mount currently for sale. Every one he had has snapped like mine.
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Damn dude, thatās a lot of broken mounts. Do you ride cobblestone streets? what kind of trucks are you running? Iām tempted to send you one of my mounts just to see if it can survive the gauntlet 
Are you going to replace those motors with same or go to a different brand? In looking back at the photos you originally posted that is a badly designed bell.
Is the bell replaceable or are the motors toast?
i just ran through MayTechās catalogā¦ those are totally maytech OEM motors. Theyāll do a lot of things for you at the 10-20 qty range and theyāll do even more for you at the 100+ quantity range. Iāve spoken with them in the past about OEMing motors from them. A LOT of people do this because they will do laser etching of your design into the can, keyways, snap ring grooves, color anodize, hall sensors, just about everything, and theyāll do just about everything but color anodize in short runs.
Iāve never seen motors break like this though, thatās really weird. Of course Iāve never used Maytech motors either. Iām still not convinced theyāre of any reliable quality.
Yup a lot of broken mounts frustration and wasted time!! Thatās only like half of them 
I resorted to making my own mount made in fully from steel
I ride everything NYC has to offer. Not too much cobblestone though. They are caliber v2 trucks. I do ride very hard, strong acceleration and braking. I would be down to test your mount.
Iām going to go with a different brand I think. most of the parts are easily replaceable except the part that broke. the motors are totally fine but with the mounting plates reduced strength and only 3 screw holes left to use, I think i have to get new motors.
Even Tacon and Rspec has that endbellā¦Never happened to me or anyone I ride with.
Iām thinking it has to do with something else entirely.
Could be vibration/heavy/cobble stone?
Belt always adjusted too tight?
Contact with truck/deck/road?
Overtorquing all of your hardware? Do you use loctite yet rather than just leaning into your wrench?
Maybe even manufacturing defects in specific batches.
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Ever since your mount broke i have been careful not to over torque anything and i always use loctite as stated above.
Maybe tight belt i was thinking also. but my other motor (sk3) is running same tightness and nothing happen to it.
NYC has the shittiest streets ever so it could be that. I donāt really ride on cobblestone.
Never any contact with the road as i could tell by not seeing any scuff marks on the motor.
Maybe a manufacture defect. They are the same manufacture of TB motors and zboard and metroboard.
They did have other defects in previous motors i got from them. like cir-clips that wouldnāt stay on and wrong length bell that kept movingā¦
Either way i would expect the motors and motor mounts to be strong enough to handle all these conditions. They should be way stronger than we need. Not just strong enough to hold under ideal conditions. The clear weak point is the thin metal where the screw is and it is a common enough problem (under some hard conditions) since it happened twice in exact same location.
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Pretty good chance my mount will fail under your conditions, but Iām interested enough to send you one - what is the distance center to center of your bolt pattern?
The design of mine is exactly the opposite - I went with softer aluminum so it can flex a little bit under stress. That might save the bell, but could also be prone to belt skip under harsh acceleration and braking. I use chain drive so I donāt have that issue.
I have the standard holes like TB motors. If its compatible send it over to be destroyed lol jk maybe it will survive 
NOTE: The videoās audio is out of sync
Hey folks.
So I finally uploaded the video of the motor destruction. Now as you may remember our video file got corrupted and we have only manage to recover 90% of the video. However the audio is out of sync.
So here it is!
Itās sad I could not sync the audio. Hope you will like it guys!
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Guysā¦ get a vise for gods sake! Also, another thing that hasnāt been mentioned is plastic thermal stress, that can cause thin aluminium castings to become brittle. Also @Mikeomania12 could you post a closeup of the broken part and the area where it snapped, it would be good to see if thereās any pores in the casting.
Thank you. Almost every motor iāve ever used has that bell design and none of them have ever broken that way. In fact the only damage iāve ever seen to a motor is yanked out phase leads.
This kind of damage has to be the result of special circumstances and iād love to know what they are. Or it is the result of a bad batch of motors with shitty aluminum.
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NYC streets are unforgiving.
ā¦just like everything else in the city 
Trust meā¦The Santa Ana riverbed has a blend of anything NYC could throw at a board and we ride our boards there all the time.
The difference is that you guys in Cali go to places to skate where pavement like NYC, we ride to places that are like Caliās endless run of the mill smooth streets! ha ha ha!
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Ok sorry been super busy this weekend, @ccostel thanks for the video and your test to break it. I think you should screw it to a mount and then try to pull it off.
@chinzw I dont know about thermal stress since the motor never gets hot. But view the close up below.
New updates are that I have broken a third motor with a similar design from the same manufacturer. Im getting a better idea of what causes this since i was able to brake this motor in just a few rides.
First common issue with these 3 motors out of the box, they make a weird screeching (that isnt the normal one) while braking very hard. sounds like magnets rubbing the stator for a short time till i lay off the brakes. So i decided to keep doing this and short stop more often. The sound was constantly only during strong braking. Then the next day i realized that the place where its usually breaks is becoming uneven/bent a little.
Next day I had to short stop on some cobblestone. (which i rarely ever ride on since iāve memorized all the newly paved streets) Then I checked the motor to see if it survived. Sure enough the piece was completely broken now.
My theory is that under hard braking with low gearing and strong vibrations and tight enough belt is enough to bend the motor ācanā so that its magnets rub the stator and make a weird noise. This constant bending and pulling on the motor as well as the weight of this heavy motor being pulled towards the ground during vibrations will eventually fatigue the weakest point being the motor cap that hold the motor to the mount. It need to be stronger since this part is the only thing attaching the motor to the mount and must withstand all these forces.
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I donāt see any air pockets in the casting, but it doesnāt look great either. Iād suggest in your case it might be worth looking for a billet machined motor since the cost might be higher, but it wont break like that every other day.
Is your mount reversed? It looks like the motor mount plate is on the wrong side of the truck clamp plate, and your belt and pulley are pushed out to the end of the motor shaft. That extra leverage on the motor shaft could be causing extra stress on the motors inner mounting hole causing it to snap.