Tandem Cycling - Newbie Tensioner Question

I'm close to having time to TLC the Sekai we got a few weeks ago. I"m wondering how tight the chain tensioner should be. Is there a set amount of deflection per distance between the chainrings, or is it more of a "feeling" where you just fiddle with it until it's okay?
Thanks for being patient with my newness.

I"m wondering how tight the chain tensioner should be.

The rule of thumb is to provide just enough play to ensure the sync chain doesn't bind during any part of a full rotation of the cranks: about 1/2" of slack along the top run usually accomplishes this.

If you find the chain is tight at some points and slack at others, loosen the timing ring bolts a bit and cycle the cranks a few times then retighten the rings to re-center the timing rings.

You'll also want to make sure your tensioner is directly in line with the timing rings.

Finally, if you find that your sync chain drops off when you hit bumps, etc... with that 1/2 of slack you'll need to go ahead and adjust out the slack with your tensioner. When this happens chances are the frame is simply flexing enough to create too much slack and the chain is derailing at the tensioner's idler wheel.

Thanks, that makes sense. I've also noticed that the sync chain (that's the front one, right?) kind of...rolls...as it comes off of the back sprocket and rolls back onto the front. That is, one side lifts a bit at the back, then comes back down as it engages the front sprocket. Is this "normal"? If not, what then? Thanks again.

If I understand what you're describing...

If it only happens in a work stand with an unloaded drive (just turning the cranks with your hand), and in just one spot then you have some stiff links.

That's pretty much the situation. It's hard to tell if it's happening while I ride, as I tend to be looking in the other direction (i.e. not down ;)) It doesn't feel very rough. Maybe a little bit.