Disclaimer: You are responsible for what advice you choose to follow and the results. Common sense and Great Care are your friends. Proceed at your own risk.
Yeah, Kohinoor is pretty adamant about never taking apart your Rapidograph pen! But I’ve been cleaning my same Kohinoor pens for over 40 years. You just have to be very careful, especially on pen-sizes smaller than #1.
- Hold the empty nib (2) in your non-dominate hand, with the metal tip pointing downward. Pick up the cleaning-needle and weight assembly (1) in your dominate hand, needle downward, and gently lower into the nip. DO NOT push it in! Let its own weight be all the pressure needed. If the weighted needle (1) does not drop all the way in, lift it out slightly and drop it straight down (needle downward) trying to visualize the tiny, centered tube you must drop the needle into. Again, DO NOT press it down, as this will likely ruin the needle, rendering the pen unusable. Lift and drop over and over until it finally drops in properly.
- Once (1) drops into (2) successfully, the back cap (3) will fit over the metal end of the weight (1) and press into the nib (2). It makes a tight seal by fitting into the inside back-end of the nib.
- Thread the assembled nib into the grip (4)
- Fill the reservoir (5) with KohiNoor black ink for technical pens, or a good quality water-based ink for easier cleaning. Fill no less than 75% capacity.
- Holding the reservoir with the opening upward, press the back end of the body into the opening until there is a snug fit.
- Finally, place the ring (6) over the reservoir (5) and thread it onto the body (4), and if you have an extension handle (not shown) thread it onto the ring, making a full-sized pen.
- Cap it and store it, tip upward.
Now, get to drawing!