Reading the manual it says, if the "B wedge" is up more than 9mm, the cam chain is worn and needs to be replaced. It also says to pull the "A wedge" up, and stick a pin in it to relieve the tension to get the chain off. My problem is, the B wedge is all the way up, and the A wedge is all the way down. I can't figure out how to pull the A wedge up. Can someone help?