Bicycle Tutor

Hi guys, a friend of mine tried to adjust the height of the handlebars by unscrewing the top part ( headset I think). After doing that, turning the handlebars is not as smooth as it used to be and I can hear a grinding noice. It also "locks up" sometimes when you ride. Any ideas what this is and what can be done? Btw, it's a Genesis Day 03

it depends on the part that they actually touched. If it's a threaded headset there is an allen bolt in the top which you adjust to move the height of the handlebars. What it sounds like is that the bearings are pushing together (maybe one out of a bearing cage?) and are causing your problems.
This will show you how to overhaul a threaded headset if that is what you have - you will need to do this. Otherwise, if you have a threadless headset you will have to do something else.
But in any event, some work is needed to get your bike up and running right again.

I'm assuming you have a threaded headset since unscrewing the top cap on a threadless one wouldn't have done anything to the headset itself.
You definately want to readjust your headset because riding it as is will probably damage it. On the headset, there should be two parts on the top of the frame that turn - the bearing adjustment cup, and the locknut on top. Loosen the lock nut and unscrew the adjusting cup a little, then retighten the locknut. Watch out for the adjuster turning when you tighten the locknut. You may have to hold it to keep it in place. You want to play with this adjustment until you get it as loose as possible but where there is no "play" in the bearings. To check for play, stand next to the bike, put your front brake on lightly, and gently push the bike forward and back. If you a feel a slight distinct "click - click" that is the fork rocking back and forth becasue the headset is too loose. Tighten it a tiny amount and try again.
BTW, on most handlebars, the height is adjusted by loosening a bolt at the top of the vertical part of the stem.