I had the same problem - had to disassemble. Used pipe cleaners, solvent, and air to clean the passageways and the ways - stuff was like hardened cement in spots. Was a bit time consuming but worth it, considering what I was able to learn about the machine while doing it.
Some before/after pics, it was worse than it looks in the before, I tossed a couple of pounds of old decrepit grease when all was done. Works smooth now - I believe the correct analogy is "like a school mom's leg" ??? , to coin a phrase....)
I've been considering installing steel auto brake lines and fittings and bolting a small reservoir to the side with a plunger/pump...kind of like the one shot system - but may need to try the grease gun mod as a start...