Grinding noise/feeling around 6000rpm

[Dead Eye]

If it stops with the clutch then that's the first thing I'd take a look at personally. You can do this without removing the engine oil as well - just put the bike on the SIDE STAND (important otherwise you will lose your oil ) then remove the clutch cover and undo the 6 screws that hold the clutch springs. You can then inspect the clutch plates to see if they are worn. Should only take 10-20 mins max and it will rule it out if it isn't the case

The gasket should be re-usable but they aren't expensive if you feel like replacing it anyway and do not tighten the spring nuts up overly tight! I accidentally did this and it snapped the housing They only need to be done up to 10Nm which is basically hand tight with a spanner