I’ve just completed my first two successful fountain pen restorations on a Parker 51 aerometric and sheaffer imperial touchdown. I am very happy to have brought these pens into working order!
The Parker 51 had a broken breather tube and was barely filling with any ink. After disassembling and replacing the breather tube it now fills great with lots of ink. While the nib is not perfect it writes well enough to leave as it is.
The sheaffer imperial ii had a good sac however the touchdown filler was creating no compression. After replacing the seals and applying silicone grease it is now working great with a satisfying resistance when extending the touchdown shaft and an audible whoosh sound when compressing. I was also pleasantly surprised by the nib which is super smooth! I was just wondering whether it is worth replacing the sac even if it is flexible and working?