If its actually grinding you need to disassemble the rotor side and see what is grinding, How did you go about tightening it up, I just went through all of this I only had a torque wrench good for 250lbs then put a breakover on it and went a little more. If its even close to 250lbs or so you should not hear any grinding noise.
First and foremost we need to know what and where the grinding noise is coming from. The sprag starter clutch in our bikes is basically the same setup as ducati's which are also notorious for sprag failures.