Does your Swift Folder have a threaded or threadless headset? The NYC bikes switched around 2001 (I'm not sure if the Oregon-made ones ever did).

The threadless setup uses a collar to lock the headset, the stem riser isn't involved in headset adjustment. The threaded system uses the top nut from the headset to keep the headset locked (just as with any threadless headset).

Do you have a photo of your setup?

alex