There are usually 3 bolts on the steering assembly. Two (1 either side) at the base of the handlebar column these are usually the ones to stop your issue. Slacken them both off then align the bars. Tighten one a few turns then the other. Continue tightening one after the other so effectively when done they should both be roughly the same torque. Check by looking at the gap between the bolts to make sure it’s even. The third bolt is underneath when the bars are folded down. This one stops the headset rattling.
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=== Update (05/11/25) ===
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If this doesn’t work you’ll need a new fork assembly
There are usually 3 bolts on the steering assembly. Two (1 either side) at the base of the handlebar column these are usually the ones to stop your issue. Slacken them both off then align the bars. Tighten one a few turns then the other. Continue tightening one after the other so effectively when done they should both be roughly the same torque. Check by looking at the gap between the bolts to make sure it’s even. The third bolt is underneath when the bars are folded down. This one stops the headset rattling.