I am trying to service my headset and have difficulties in removing the bearings from the headtube. Those bearings seem to have accumulated some dirt over time and are feeling a little bit grindy. I suppose I am missing out on something here as the bearings seem to have a really tight fit in the tube and I cannot remove them by hand. I also tried to apply some slight pressure from inside with the wooden handle end of a brush with no success. Is this something special like maybe threaded into the tube? Is it even possible to remove those easily?
You can release the bearings by removing the snap ring holding the bearing race in place. At about the one o'clock position there is a gap in the snap ring, which sits between the grey and the black circles.
A (disposable) knife blade can be useful (thin enough) for prying the snap ring just enough to release it, wear safety specs.
Clean and grease the bearings then reassemble, consider swapping top and bottom for increased life.