Originally Posted by Kuma
On reflection, I think this is the problem I'm experiencing, rather than a star bolt. Apologies for my ignorance and imprecise description. I've tried loosening the bolt inside the steerer tube (I guess this is the "plug" you're referring to) with an allen wrench to the point that it turns pretty freely and seems likely to fall out itself. The piece below the bolt that the bolt is attached to, though, fits pretty snugly inside the steerer, and doesn't seem likely to fall out without some stronger force than gravity and my tapping on the outside of the headset. I may just use roadfix's proposed solution of getting a larger headcap bolt from the hardware store. I'll keep trying...
What you describe is unfortunately all too common among bike building newbs. I have to laugh because if you have built enough bikes, it has happened to most of us. I can help. You are quite right, there is likely too much pre-load on the plug to invert the bike and shake it loose. Take a coat hanger and clip the end and put a 110 degree small hook on the end just shorter then the diameter of the bolt. Fish the plug out. The barb on the coat hanger hook will grab the involute of the female thread of the plug. Pull the plug out. Now...I will give you a good tip so it won't happen again. Plug depth as it turns out is relatively important relative to screw length, proper thread engagement and not bottoming your cap collar on the plug. There are a couple of different plugs designs out there...with and without plug preload adjustment. What you do is always use the cap and bolt when setting the depth of the plug. If your plug has a separate pre-load bolt....make sure the tension is just higher then the clearance between the plug and steerer tube I.D. That way the plug will never fall down as you set the proper depth of the plug relative to thread engagement.
HTH,
George