I built a wheel with a generator, installed "The Plug" by Supernova. To facilitate this, you have to not use a conventional star nut, but use an expanding plug..I understand the concept, so that wires can trail down inside the fork. The plug arrived with no specifics on torque or technique. So I installed it. Tightened it to what I thought felt good and tight. Put my steer tube together and tightened down properly to get rid of headset bearing play.
Now, I ride the bike for a few minutes and I have to tighten the headset bolt. I'm wondering where the looseness is coming from..? Is the bolt backing out (should I use a thread lock) Is the expander creeping up the steer tube? Any input with this.
I am really happy with the setup except for this annoyance..
Thanks.
Perry

Take it apart and see if the expander moved up. That's my expectation.

From your description I presume that you have a threadless steerer setup. If so the only purpose for the cap bolt is for setting the headset preload (and holding the cap in place of course). After you are done, the adjustment is held by tightening the stem clamp bolts. For all practical purposes you could remove the bolt (and cap for that matter) altogether with no ill effect. So there is no point to being concerned about the tightness of that bolt.

The instructions, seen online, still use a star fangled nut .. you may have to realign the 'stars' to let the wire pass thru..
The gap, then you push it down further ..

+1, the starnut or expander isn't intended to retain the adjustment when riding. So if your headset is getting loose, it's a stem clamp related issue.

in the guessing, that seems a simpler thing steerer grip of stem too loose...



those carbon steerer required expansion things have their own issue .. sometimes they dont grip inside the tube adequately..

But the stem is what keeps the adjustment fixed ..

As said above, the expander bolt/plug are not the issue, it is the stem bolts on the side that hold it all in place.

Is the headset new? It could be the bearings/races were not pressed in completely, so you tightened it up ok at first but then after some riding the bearings pressed home a little more, causing some slack.

So make sure the side stem bolts are loose, tighten down through the plug so it feels nice, then crank those side bolts down hard to make sure it stays in place. (note if you have a carbon steerer you need to be more careful with torque -- but if it's a metal steerer tube (even if the fork blades themselves are carbon) you should be able to clamp down those stem bolts pretty hard.

torque specs get printed on there so you dont strip the threads out of the stem ..

beam torque wrenches , particularly 1/4" drive, are not too pricy ..