mamba max very weak braking...why?

[blueb8llz]

im using the stock radio that comes with the mini rc18, i dont believe it has a brake setting. but anyways, i used this exact radio with the vilenion system and it worked great.

i bought the mm6900 combo used so i dont know the past, but he claimed it only had 10 runs hahah thats most likely a lie.
the motor doesnt seem demagged...how can you tell anyways.
it still has plenty of power, and goes fast..havent gps yet but looks around 45+
the motor does heat up pretty fast cus im geared soooooo high especially with them big o tires. it gets to about 150 degrees in 20 mins. so does this sound like a weak magnet causing weak brakes?
how can i check if the caps are dead?