The long bolt is the bolt which sets bearing preload; it screws into the star washer. The star washer is a tight enough fit in the steerer tube to give purchase for preload adjustment.Rob D wrote: ↑18 Mar 2024, 7:34pm …….There was a top cap, but that's secured by a long bolt going down to a sort of oversized spring washer with central female thread - a 'sunflower'? See photo.
At the base of the stem, where it protrudes from the top of the head tube is a thin tube (for want of a better description), possibly the top of the drop cap or upper bowl lid (from diagrams on the net)? This has a 'slot' in it. I'm wondering what this is for? See photos. I'm hesitant to proceed further til I know how to tackle the next stage. I'll search YouTube too.
Drop cap and upper bowl mean nothing to me in the context of headsets
Wikipedia has clear diagrams of threadless cycle headsets