A. Never, ever attempt to straighten a bent blade. Aways replace.
B. If the blade is bent the shaft that it attaches to may also have been bent which means the engine is scrap.
C.The blade undoes anti-clockwise, but may be very tight now as you have hit something
D. Remove the engine oil and tip the mower on its side with the exhaust downwards.Remove plug lead and use a 14mm socket or spanner. Wear thick glove and stout footwear. Crouch down, move the blade so it is vertical and place your right boot to the right side of the blade- this will give you something to lever against.
E. With the blade removed place the mower on its wheels and with the plug lead still off, get someone to stand behind the mower and lift the front wheels clear enough for you to view under the mower. Then get your friend to swiftly pull the rope while to obseve the shaft the blade was attached to. If the shaft rotates off centre then the shaft is bent and it's scrap. If not, purchase as new blade, re-fit it and don't forget to refill the engine with oil. When you initially re-start it, it may smoke for a few minutes, but this is normal and the white smoke should stop after this time.
pleasant, August 2010