

I understand you know how to change the step length that can be changed now, yes?
Yea
You say <2mm to 5mm. My very similar machine can go to almost 10mm but it cannot keep the thread very tight.
I would die for 10 mm. I would be in to adjust the machine while sewing for any step lenght larger then 5 but 10 mm would be perfect.
This is the limiting thing, the machine, every part, is designed for sewing a length of 2-8mm or whatever. A longer stitch step would need a complete change and probably a stronger motor.
I can change gearings, leverages and axles if I understand what to communicate. I am not bound to the current chassis and motor. I can construct a chassis afterwards rezpecting current alignments within nm.
By moving the knob or lever that changes the stitch step length, you will see what is going on.
I circled the change in blue. Leveraging the handle could be the case but axles wind on their own. It is a mind fuc* which can only be put in perspective by Engineers, imo.
I fear this may be the case but since I am not an engineer thought about pulling some opinions here thumbsup