400ex makes a grinding noise after running

Ok so I just bought a 1999 400ex and it ran pretty good and then all the sudden I was riding it like locked down or somthing and I put it in the garage and it had other problems with spark and stuff so eventually I replaced all the wiring on it with a whole new wiring harness and everything and it starts really hard and I got it running last night and it ran good for about 3 minutes and it just shuts of randomly and makes a screeching/grinding noise and I already checked the timing and the clutch can anyone help me?