Hi there! Sorry to revive a dead thread but I stumbled upon this looking for info on timing my Mason (re branded consew 146). I have a bit of info for you if you need
When I got my machine it had a three step cam in it. I got a new regular cam off a place in Toronto for a pretty penny. Anyhoo, Sail rite has a video on how to replace them and it worked like a charm. I just did it in reverse. I'll add the link at the bottom.
As for the flywheel being stiff, I think that's just because it's newer. My 20" Mason spins beautifully, though it's really old. But I have a newer 30" consew 146 and the flywheel is like how you describe. Tbh I hardly use it as with the extra length and the stiffness it's a bear on your shoulder. So I think it's just going to be time on that one.
Hope you got your machine sorted in any case!
https://m.youtube.com/watch?v=s1fMR4VZ-Us