The primary sprocket nut is 1 - 1/8 inch.
A lock nut should go on a bolt before a washer or the nut.
It is behind the sprocket shaft nut.
straighten the bent washer, Did you buy spare lock washers? remove the nut, 1-1/4" or 32 mm, I stand on the rear brake loosen the chain adjustment work the front sprocket out if the chain, it's tougher with a 14 tooth install new sprocket Don't forget to bend the washer back over the nut if you have the stock chain it might not have a master link so i cut mine but there is a way to take it off without cutting .
160 foot pounds
The front compression nut is right handed, however the nut hold the clutch hub is left handed.
25 ft lb
Press down the rear foot brake and use a breaker bar or large ratchet with correct size socket to loosen nut on front sprocket. (never use impact wrench NEVER EVER!)Once you get the nut broken loose. Unclip your chain and put the gear in neutral and pull the chain through and set it aside. Put clutch in first gear and continue to ratchet loose the nut. Loosen nut all the way. Change out the sprocket. Tighten nut as much as you can with bike in gear. Put your bike back in neutral and feed your chain around the sprocket pulling it through and resting both sides of it on the rear sprocket where you will reclip the master link. Meeting both sides of the chain on the rear sprocket will make it easy to clip as the rear sprocket holds your chain for you. Once master link in chain is clipped. Step on the rear brake and crank down to spec lbs on the front sprocket bolt. If you don't know the foot lbs.. just make sure its real tight. Your done!
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.
no.
top speed of a yz125 in mph
Yes, if one has been fitted.