Motorcycle Repair: front sprocket, rear axle nut, countershaft sprocket

Question
on a 99 yamaha r1, it has a 16t front sprocket.
im wanting to put on a 15t,however,
i cant seem to get the nut off.
why does the bike roll back & forth,in or out of gear?
would an air impact help, or would it damage
anything?
i also assume that this has a reverse thread?

Answer
Hi Michael,

1) Loosen rear axle nut and adjuster screws
2) Spin adjuster screws all the way in (clockwise)
3) Remove shift rod and shift arm.
4) Remove countershaft sprocket cover (3 bolts)
5) Bend lock washer back (use a flat tip screwdriver)
6) Use 36mm socket and breaker bar to remove nut (Have someone step on rear brake pedal to lock rear wheel, I did not have to, just put her in first gear)
7) Pull off countershaft sprocket
8) Re-assemble

Respectfully,
Mark Shively