My sprocket was so stuck on one of my bikes that there was no way that I could get it off with a normal socket wrech. Impact gun did not work either. I ended up putting the chain on and turning it until it got stuck and just jurned it until it came loose.
So that sprocket might be quite stuck if it has not been removed recently. Not sure about the pivor bolt nut size though
07' YFZ 450
PEP PB1 front and rear, Lonestar +2 A-arms, HMF Competition exhaust, Precision dampner ,HST ported head, Lonestar +2 axle, Flexx bars, Powermadd handguards, Houser +2 stem and clamp, OMF beadlocks, DG bumper, Pro design Intake, Long range tank, GYTR nerf bars
04' YFZ 450, PEP PB1 front shocks, Lonestar +2 A-arms, Pep rear shock, Airtime +2 axle, Airtime +1 stem and clamp, Flexx bars, Pro Circuit T4 slip-on, DWT rear beadlocks, GYTR front bumper, Hyde skidplates, Long range tank