I've torn the fork apart, but can't seem to be able to remove the cartridge from inner tube, for thorough cleanup. I did unscrew the base valve nut, but it doesnt come off. I should probably hold sth inside the fork tube, but while turning the base nut, nothing else seems to turn inside the tube. Also pressing the rod doesnt seem to push the base out. Theres a triangular unit, called cylinder tube cap, that the rod slides through, and is the only visible thing from top. Its a plain, single chamber fork.