When a cartridge pen has been left uncleaned for a long time, ink residues can dry and impede flow; a simple piston converter is then often not enough. A proven method uses a Pelikan large-capacity cartridge and a so-called ear syringe from a pharmacy, e.g. size M for around 3.45 euros. Cut the rear of the cartridge open and clean it, then attach the ear syringe to the cartridge and fit the assembly into the pen as a normal cartridge would. To clean, hold the nib in water and squeeze the rubber ball; this loosens even stuck ink residue from the feed. The method is not limited to Boheme or Montblanc but is suitable for any cartridge pen.
Related pages on fountainpen.de:
• Montblanc Bohème — model overview: https://www.fountainpen.de/boheme-en.htm