my lawn mower hitted a big rock and my blade got twisted. After that it doesn't start, thogh I change the blade for a new one. Sears told me that I have to change a small part (by the way, I don't know to say it in english, but in PR we call it "cuña"). I was trying to figure out were exactly goes. If you can help me with any engine diagram I'll appreciate a lot. See Product picture below, I took a shoot of it.