As far as the grinding goes I bet the idle is too high. Look on the handle bars and follow the cable down out of the throttle housing about 2 inches. There is an idle adjustment that you can get to quick. Turn the idle down then try the reverse. Check the gear oil first. Its a yellow handle dip stick above the rear foot brake lever on the right side.

Tranny is loud. But check to see if the oil is up to the fill mark.

Look on ebay for brake pads. i got all 3 sets cheap. Then you have to bleed the entire system if it was sitting. Mine are fine now.

Ride it too. I purchased mine for $2000. its a 2x4 and needed very little.

Also check the oil pump cable like i said before. If that is not working dont ride it. You could burn up the motor. I got lucky.