I'm blowing the cobwebs out of my mom's 1986 Ward's (Happy Sewing Co) machine. I have been watching videos of setting timing:
adjust timing until the hook passes through the scarf...
...and how to set the needle bar:
adjust needle bar height until the hook passes through the scarf...
(I'm paraphrasing)
It sounds like you could take a perfect machine, then lower the needle bar 1mm, then compensate by delaying the hook 30 degrees, and you'd have the hook passing through the scarf at the correct spot... yet it would be all wrong.
Is there a way to set needle-bar height independent of the hook timing?
Like, obviously the needle needs to rise a few millimeters to make the slack thread form into a loop behind the scarf, ready to be caught by the hook. Is that amount of rise kinda-sorta consistent across machines from a given era?
We have a Tern GSD (both wheels are 20"). I think having the back wheel smaller is important if people are going to sit on top of the rear rack. The smaller front wheel does allow more stuff on the pizza rack. But I also have an old 26" MTB with pizza rack, and it can carry plenty of camping gear up front, even with the 26" wheel.
The down-side of the smaller 20" wheels for me is in snow (not a problem for everyone!). I crashed once, even with studded tires, while I'd ridden that MTB with studded tires all winter for years without falling. Also, there is only one studded 20" tire available, and it is not knobby enough for me.
Having both wheels small definitely make it easier to store. I had an Xtracycle Free Radical attached to the MTB, and that bike was long and hard to park.