I have never seel felt bits in tensioners, only on the spool pins. These days there's probably more help and advice to fine, since the w.w.w. has grown enormeously since the machie were put in storage. I seen these machines both on US bogs as well a mentioned on German sites. For the top tesion I would expect something like two or three chromed metal disks, the tread would slide in between two of them, and. The arm on the spring should be placed so there's a bit of tension on the thread as the lifter arm drags the thread. They can be a bit difficult to assemble right if there's noting to go by. Usually you can get replacement springs for these old machines.