I just bought it for 800 bucks, runs well it seems. I found that when going in reverse, or just in neutral going backward a couple miles per hour or more, when applying the front brakes it makes an odd grinding/squealing noise. I changed the pads and rotors but still does it. Not sure what it is, anyone have any ideas?

 

Brake lever operates both front brakes along with pressure on the rear brake caliper.Could be a stuck caliper piston in the front or even the rear caliper pads making the noise against the rotor if the rear piston is sticking. Plus there is an adjustment on the manual brake pedal that a lot of people forget about also. Loosen the lock nut on the caliper body lever and while holding the brake pedal turn the 7/16" screw inward to put pressure on the piston which also raises the pedal. Stop when the bottom of the pedal is about 1/2" off the floor board and tighten the lock nut.Try it out and see if it helps. If not you may have to isolate whether the noise is from the front or rear and see if it needs a piston/seal kit. Plus on the front brake calipers the small 5/16" allen hex bolt needs to be turned in until you feel a slight drag from the pad against the rotor,then back off 1/8 turn. This aligns the main braking pad and caliper bracket with the rotor.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

This might be a stupid question. If the caliper was sticking, wouldn't it stick also going forward? I have to change the rear pads next so who knows whats there lol

 

Yep,if a piston is sticking it would stick in forward and reverse,but usually the noise comes when you change directions opposite of what the pads are used to running 90% of the time which is reverse. This is when they run against the "grain" so to speak and can grind or squeal. Plus even a slightly warped rotor if you didn't change the rear rotor along with the fronts,can do the same thing when in reverse.Had this happen a few times,but most of the time it was on the rear caliper piston or simply the way the rear rotor is mounted.It's held only by the transmission shaft splines and a circlip and not bolted on like the more stable front rotors are.This little free floating in the rotor itself can tend to vibrate and cause squealing from the pads.The 96 and 97 Sportsman 500s were bad on rear rotor squeal in reverse.After you change the rear pads you can also drive it in reverse a few times and push the brake pedal down hard for small intervals to see if this helps burn in the new pads and quiet it down if the rear brake is where the noise is coming from.May just be worn pads squealing against the rotor since you didn't change them out when you did the front brakes.