I am in the process of changing the sprocket,its on and Im having a rite old faff trying to torque it down to 120nm.

Im sat on the bike,apply both brakes and as Im left handed feel ok tightening the nut up...its moving but at 98 nm Im worried that its not tightening...

Its in neutral so no fear of damaging the box.

I backed off from 120 and thought Id do it in stages...

I used an electric impact driver to get if off with no worries and again to put it back on till it 'rattled'.

Any suggestions?