Break of Clutch Problem

I just bought a 2007 450 King Quad with about 1000 miles/90 hours. After riding it around a little there seems to be a problem with the brakes or something. If you brake really hard, using either the hand brakes or the foot brake, and then hit the gas again, it gets like stuck and then pops off and the tires squeal. It is like really jerky.

I brought it in and the tech said he hasn't seen this before. He took apart the brakes and said there was some wear on the drums, so we replaced that, but it is still happening. He said the rotors looked good.

My next guess is maybe the clutch or something?

Anybody have any ideas or had this happen?

Thanks.

When you slam on the breaks the belt gets a little loose on the pulley and when you hit the gas it kind of grabs.

Its a normal thing that I would not worry about.

I raced for a long time with no issues.