How to Tighten a Headset on a Mountain Bike Like a Pro
To tighten a headset on a mountain bike, start by loosening the stem bolts and then use an Allen wrench to tighten the top cap bolt. Make sure the top cap is sitting flush with the top of the stem. Next, tighten the stem bolts back up and test the tightness of the headset by holding onto the front wheel and rocking the bike back and forth. If there is any looseness, repeat the process until the headset is tight and secure.