Hi welcome to the forums. you best bet is to eaither contact the manufacturer, a shop that sells these or the seller. it is very likely that it will take a 1 1/8" HS but there are so many variables here. can you post a few pics? is the ends of the HT flared? maybe it takes a hidden style headset.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk