If the front of your bike feels very heavy or the bike just gets not so easy to control, the most likely problem is the headset. What you should do now is adjust the headset in proper and you could enjoy riding again.
There are some instructions for adjusting a threaded headset. Basically this is an older style headset. But it is still used today on some bicycles as like a classic style. It is called the "threaded" headset because there are threads on the fork's steerer tube where the headset threads on.
Step 1: Check the current adjustment.
Let's start by checking to see if the headset is currently too loose or too tight. First, you cannot actually test for it when the bike is stationary. So all you need to do drop the front end. You can hear that knocking there and also put your front brake on which for me is the right one. Gently move the bike front to back and you should be able to feel some playing actually because this one is particularly loose. You can see the play in the top headset race there.
Now the good news is a really simple problem to sort out on your own. You don’t really even need any complicated tools. All you will need is an Allen key to undo the bolt on the stem cap here and another Allen key to undo the stem bolts on either side here. Now in this particular case, they are both four millimeters. That is the only tool I will need for this part. Now preferably, you also want to have some kind of torque range ready for. When you do these stem bolts back up, just make sure you have got them at the correct time. It is not tight not too loose. That is quite important from a safely aspect. But we won’t need that until the last part, so we can put it to one side just for the moment.
Step 2: Loosen the locknut.
So step one is to loosen your stem bolt. And this is very important because what we are going to be doing in a minute to tighten the headsets. Turn the screw there on the stem cap and essentially what does it’s pulls the forks up. I either steer it to you is go away from the forks absolute a head tube out to the top here which the stem is clamped onto and pushes the stem down compressing and centering the headset. So if you don’t loosen these stem bolts, you are effectively trying to push a stem down which is clamped tightly to the fork steerer tube. So just get your Allen key loosen all of the bolts. There are two on here. Some of you might have one and then we are going to put our Allen key into the stem cap here at the top and give it a turn now. This is slightly trials and errors in that you don’t want to cover tighten it. If you do, you won’t have free movement in the headset. But if you don’t tighten it enough, you will still have some kind of play so I reckon about there is good. You can test it by rocking it again and giving it a quick turn to make stiff on either side. And once you are happy with that, all it is a case of doing the stem bolts back up after making sure that your stem is still aligned with the front wheel. So I am going to use torque wrech for that you are probably find on the stem the maximum advised by the manufacturer. So on here, it’s six Newton meters. It’s advisable to not tight it all the way to six on just one side. You want to do the bolts up a little bit at a time. And I am going to it to five Newton meters because as I said the recommendation is for the maximum amount. So got no more annoying knocking sounds doing the front brake test and rocking forwards and backwards cannot hear or feel any play. And I turn it. Importantly it’s completely free. It’s not stiff at all. So that is a good job done.
Step 3a: If the headset is tight...
Turn the adjustable cup (right below the locknut) counterclockwise to loosen it. Start with a 1/8 to 1/4 turn, which is usually enough to loosen things up.
Step 3b: If the headset is loose...
If you find that no matter how much you tighten your stem cap bolt here, there is still some play in your headset. What you might find is that your fork steerer tube is a little bit too long. What you should find then is that there are a few millimeters gap between the top of your stem. Now if that gap isn’t there effectively, what you are doing when you tighten this bolt is just pushing that headsets cap down onto the fork steerer tube and not tightening the headset itself. So there are couples of solutions to this problem. The first of which is to cut down your fork steer at you but that is quite a big job. So a much more simple solution is to invest in another headset spacer. So you can either put that undermeath your stem or on top of it if you want to make sure you are in exactly the same position on the bike. And that should solve your problem. On the other hand, though if you find that you can tighten your headset, so there is no play but you cannot do so without finding it’s very stiff to turn your bars and it might be that your headset needs a good clean and service. And actually that is something you can do yourself as well.
Step 4: Retighten the locknut.
Now that the headset is adjusted, retighten the locknut to lock in the adjustment. (Be sure the stem and front wheel are still lined up, though!)
Step 5: Check the adjustment.
Repeat Step 1 to see if the headset now turns smoothly without knocking or binding. The key is to keep the headset just tight enough so that there is no play back and forth.
Step 6: Readjust.
Repeat Steps 2-5 if the headset still seems tight or loose. It's not uncommon to readjust 2-3 times to be sure you got the perfect adjustment! But if the headset seems right, go ride!