Franco:
From the photos, the kart needs some TLC. First off, I’d get some brake cleaner and spray it inside of the calipers. It looks to me like the brakes have some build-up and if you haven’t been out they could just need to be “freed up”. Lots of rust on the rear axle/brake rotor so I’m guessing it’s just bound-up inside. If you are comfortable, I’d take the entire rear end apart and clean it very well. Start w/ a Scotch Brite Pad on the axle and end w/ some 0000 Steel Wool. WD 40 is great but be careful not to get any on the rotor or the pads. Speaking of the rotor, it is pretty glazed up…get some emery cloth and clean the rotor very well. Basically, scrub it down to a ‘silvery’ color; fronts as well.
The hoses…you need to replace them. I’m guessing they hit the exhaust pipe or something?
You’re not too far from IMI and I might also suggest taking the kart there for general maintenance and a good once-over.
Good luck!
Troy