I just bought a Consew 206RB-5 and looking in the owners manual it says:
"THREAD:
Cotton, synthetic or silk thread can be used according to your purpose.
*Always use left twisted thread for upper (needle) thread, but you can use either right or left twisted thread for lower (bobbin) thread."
I have alwasy been a hand sewer, but just bought this machine last week to use on larger items such as totes, etc., plus I got an amazing deal on it. I have used Maine Thread Waxed Poly since I started, but for the last year have been using Japanese Vinymo thread for a lot of my projects. It's beautiful thread, vibrant, and soft to the touch. It's unwaxed, which I don't mind becuase I have my own wax and don't mind waxing it. That's what she said. And since it's unwaxed it can be used on my machine as well. I like the ruggedness of Maine but it can be too waxy sometimes, which is a common "complaint" about it, but I don't mind that too much. Vinymo comes in tons of colors as well, which is really great. It's also available in large and small spools for US based suppliers.
Hope that helps a bit.