Unless you are doing something that needs good low speed control (like crawling), or is goverened ny regs that prevent you using BL, then I'd just buy another Brushless rig. It's cheaper in the long term, more efficient and lasts way longer. What's wrong with yours? Has the motor died or the ESC?
Brushed are a PITA in comparison, what between keeping the brushes serviced, keeping the commutator trued, and cleaning all the crap out for the can every so often from the brush wear. They'll never be as good on batteries as a BL and always take more looking after, all of which costs you money. A Truing lathe alone will cost you 140-180 US and a lathe tool another 100-140 US (these prices are a bit broad because I'm in the UK and I'm guessing from Google Shopping). That alone is enough to buy 2 Brushless kits. Brushes aren't expensive, maybe a few US a set, but if you use it often and drive it hard you'll eat them fast. very so often you'll have to pull the whole armature out and renew it which costs about 1/2-3/4 of the cost of the motor.
I went from Brushed to Brushless on my Wheely King and frankly would never go back. You get more power and speed and longer runtimes and over the lon term it's cheaer to run. Who can argue with that?
