Adjusting your Headset
-6mm Allen Wrench
-8mm Allen Wrench
1) The first thing you'll need to do is loosen the stem bolt with the 6mm Allen wrench. This bolt holds the stem and the fork together. You'll only need to loosen it about 1/2 to 1 whole turn. (See image 1)
2) Next, loosen OR tighten the top cap bolt with the 8mm Allen wrench. ONLY LOOSEN/TIGHTEN THIS BOLT IN MICRO ADJUSTMENTS (1/16-1/8 turn).
(See image 2)
3)Once the top cap is adjusted, tighten the stem bolt again.
My headset is too loose...
If your headset was tight and you loosened it proceed to step 4a.
4a) Test the steering by lifting the bike (you may want a second person to help) so that the front end of the bike is slightly lower then the rear.
5a) Try to rotate the handle bars
6a) It should try to center its self. If it does not or still feels stiff, repeat steps 2-4
7a) If you're happy with the adjustments, you'll want to tighten the stem bolt to 13N*m if you have a torque wrench. If you do not, then you'll want to tighten it "pretty darn tight"
My headset is too tight...
If your headset was loose and you tightened it, proceed to step 4b
4b) Test the steering by squeezing the front brakes.
5b) Rotate the handlebar 90 deg.
6b) While still squeezing the front brakes, gently rock the bike forwards and back. Try to "feel" any looseness in the headset. If the headset still feels loose, repeat steps 2-6b.
7b) If you're happy with the adjustments, you'll want to tighten the stem bolt to 13N*m if you have a torque wrench. If you do not, then you'll want to tighten it "pretty darn tight".
Checkout more self help here