Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Fantastic engine.

I recommend trying to pin point the knock.

Thicker oil on that joint may be the fix or even grease. I have synthetic crystal clear grease for this purpose.

A noninvasive trick to handle it is to use the flat tape style plastic floss for teeth.
With that you can wrap the pin to make up slack or slop. It's soft and gentle and makes the engine purr.