As far as I know you don't remove them until you find the right height as you then need to cut the steerer tube to make it a permanent change. It does look 'silly' to some snobs but I would only cut if you don't plan on reselling the bike later on.
So undo the expander plug's allen screw until it almost comes free of the plug. If it comes out, screw it back in 3 turns. Then tap lightly down on the head of the allen screw to release the taper in the expansion plug. Pull it all out.
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The star nut is the threaded insert inside the steerer tube. The headset spacers are round spacers that sit below and/or the stem.
If you do want to remove the star nut take a look at this link
http://forums.mtbr.com/showthread.php?p=1189999
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Cashback on wiggle,CRC,evans follow the link
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Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
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£1.25 for sign up http://www.quidco.com/user/491172/42301
Cashback on wiggle,CRC,evans follow the link
http://www.topcashback.co.uk/ref/MTBkarl
Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
Instagram: https://www.instagram.com/ben_h_ppcc/
Flickr: https://www.flickr.com/photos/143173475@N05/
Dales.