Headset expander/compressor not compressing headset

[nickAKA]

The wife's new bike (Wilier) came with an expander plug for the steerer tube and I'm struggling to get any sort of 'load' onto the headset bearings - I can't see an obvious way for it to compress, I assumed it must pull down the top cap after it had expanded and you then nipped it up but I can still turn the spacers underneath the stem and there's no more adjustment on the centre bolt... am I missing something obvious here? I've seen some of the expanders are two piece assemblies where you tighten the expander then the top cap screws into that, but it's definitely 1 piece. I've ordered some carbon grip paste in case it's sliding up the steerer tube but I'm wondering if I'm missing something obvious here? TIA...

 

[T.M.H.N.E.T]

With the top cap off is there a gap between the top of the fork and the top of the stem

 

[MichaelW2]

There are two gaps you need.
The top of the spacer should be higher than the top of the steerer.
The top cap should not make contact with the plug when you compress them together.

See

View: https://m.youtube.com/watch?v=lM4iddLaL8I

 

[nickAKA]

Yeah I went with the 2mm gap theory when I cut the steerer down but I'll double check it, I'll put a bigger spacer on the top to start with and see if it's any different. I suspect the bung is slipping.