How do you change the chain drive sprocket on a stihl 051AV. There is not a chain break so the sprocket spins with the retaining nut.?
you have to prevent the crankshaft from turning when you loosen
the retaining nut. the nut is probably left-hand threads(loosen by
turning clockwise). remove the spark plug, turn the sprocket (and
crankshaft) to the left until the piston is at the bottom of the
cylinder, insert enough nylon pull starter rope into the spark plug
hole to fill the cylinder, turn the sprocket to the right until the
rope is compacted enough to prevent the piston from moving, put a
wrench on the nut and tap with enough force to break it loose.
replace the sprocket and use the same process in reverse to tighten
the nut, don't go nuts tightening, it will tighten itself as you
use the saw. a dealer might give you the correct torque specs.