Onoto lost is suction

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My plunger filler Onoto has lost it`s ability to take up ink. During a cleaning and flushing something happened and it no longer has the suction sound when the plunger is pushed in. I had it in for renovation about two years ago, new rubber seals and parts that needed replacement. I can`t see any way to open the pen. The repair guy of course had it opened but it looks like there isn`t any easy way about it?


Is this a common problem with an old Onoto? I regret cleaning it too vigorously, I should have kept to only a light flush. How do I go about it?



...using my Pelikan for now...