I love my Japanese made Platinum pens but I had a couple of their convertors that were terribly balky and hard to twist. Here’s an easy fix. You’ll need some silicon grease, and that’s all. Please be careful to only put the grease on the convertor piston above the ink seal. Make sure you wash your hands extremely well before touching the nib, feed, etc. If you do that, you’ll find this very easy.
Unless you want an inky mess, do not try this on an inked pen. Did I learn that from experience? What do you think? Gently take the convertor apart, trying to remember how it goes together (I’ll review it, but it makes it easier if you try to remember.) I crank the piston all the way up to the top, as far away from the nib as possible. Then I take off the metal housing (3). At this point, you can just grease the extended piston (1), and put it back together. But sometimes the top two pieces (2 and 4) pop out. Don’t panic! It’s ok. You’ll actually have a better functioning convertor if you grease 2 and 4 where they meet.
So if they did come out, just take part 2 and push the ribbed part (to the right in this photo) up through the larger opening in the metal housing (3) until it extends out the smaller opening. Then pop #4 on top of part two (where it’s inside the housing.) I’ve never noticed a right side to part 4, but just in case I’ve been extremely lucky, just flip it if the first side doesn’t work.
Now hold the combo of 2, 3, and 4 horizontally, and screw it over the piston. It helps to do all this horizontally so parts don’t shift but you may find another orientation works better for you. Your convertor should now work smoothly (unless something else is wrong, like a bent piston or missing piece.)
Congratulations! You’re now a Platinum pen convertor repair rock star.