Also. (This might sound obvious) Please make sure your belt isn’t too tight. And make sure your wheel nut isn’t too tight… do you use a bearing spacer?
The wheel should feel like It can rotate without too much resistance from the motor. Too tight and you put extra load on motor which equals heat.
The best way to judge belt tightness is to loosen it fully. Now Slowly increase the tension until you feel a difference in tension at the wheel… The first moment the “feeling” of resistance appears at the wheel you have now just reached the correct tension. There should be no feeling of tightness/resistance.
I had another similar problem just last night, reduced power with no obvious reason. I checked literally everything but couldn’t find the cause.
I eventually swapped out my R-SPEC for a spare one and the problem was solved. I haven’t opened it up yet. A bit disappointed the motor gave out so soon, these are not cheap.
Sounds like your esc is overheating. Can you provide the following:
Your weight
Gearing ratio
incline of hills your riding and length of hills
Given that you’re able to hold your motor for ~3 seconds, I wouldn’t say it’s overheating as much as your ESC is. I’ve had my single motor uphill get pretty hot, but it was still running. I wasn’t able to even touch it for a second, the thing was burning!
Looks like you’re using an Enertion wheel pulley? If so, thats 36T. Whats your motor pulley? I think your riding environment might be too much for a single 55mm motor.
One more thing to check is your belt tension, if it’s too tight it’ll definitely cause overheating. Try to be as loose as possible without belt skipping at hard brake/acceleration.
I know you’re recording video for testing but try not to throttle when the motor is chugging slowly like that. You can and will break your motor and/or VESC. Try mounting your VESC outside somehow and going for a ride. When you notice the slow down try to see if your VESC is hot. Normal cut off start is 80 degrees.
I’m guessing that if you try mounting it outside you won’t see the problem as early since it’s not insulating heat within the enclosure, and would be air cooled by just riding.