There are two bolts in the center of the handle-bars. One bolt (on some bikes this is actually 4 bolts) is used to clamp the handle-bars to the handle-bar-stem. You can see both ends of this bolt. If you loosen it, you can tip the handle-bars up and down, but not raise them. The other bolt you can only see the head of. Loosen this a couple of turns (don't unscrew it all the way) then give it a tap with a hammer. You will then be able to pull the handle-bar-stem completely out. Do this so that you can see the wedge-shaped nut at the other end of the bolt. You should also see a mark on the stem that indicates how high you can safely raise the stem. Put the stem back in to the desired height and tighten it back up. Good luck.
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There are two bolts in the center of the handle-bars. One bolt (on some bikes this is actually 4 bolts) is used to clamp the handle-bars to the handle-bar-stem. You can see both ends of this bolt. If you loosen it, you can tip the handle-bars up and down, but not raise them. The other bolt you can only see the head of. Loosen this a couple of turns (don't unscrew it all the way) then give it a tap with a hammer. You will then be able to pull the handle-bar-stem completely out. Do this so that you can see the wedge-shaped nut at the other end of the bolt. You should also see a mark on the stem that indicates how high you can safely raise the stem. Put the stem back in to the desired height and tighten it back up. Good luck.