Originally Posted by
CACycling
First, I'd remove the cap and check instead of being "pretty sure". Assuming the stem is above the steerer, I'd straddle the bike, lock the front brake and rock the bike forward and backward. This is a much better than the "drop test" to check for a loose headset. If it is knocking, you don't have adequate preload. It is pretty easy to feel where the knocking is using this method.
Thanks so much for your help. So I just checked, the stem is above the steering. I can't feel any knocking when I straddle and rock the bike. I started playing around with different preloads by tightening the cap screw by so much more each time I reinstalled the stem. I could feel/hear less noticeable knocking as I applied more torque to the cap, but I'm afraid to damage the star nut. Thoughts?