Shqizy,
I always set my radio to 90% then back to 100% thats with a Futaba 3pk Fasst system. You said that you have tried other caps what one came with it? Did it come with the four caps mounted on a circuit board? Others have issues with weak brakes and other odd things by not using the "big" cap. I have to agree with the other guys your gearing seems a little high and I would aim for a max temp of around 65 - 70 C, 90 C is really hot and most likely will cost you a motor or more.
Hope that helps,
James