AlZilla

I got a Singer 14U64A on the Goodwill site and after a lot of learning curve, I seem to be zeroing in on a serged seam that looks like what I see online. But ...

The left needle doesn't seem to have a stop when I'm inserting it. In fact, it doesn't have a stop - it will run in so far that the clamp won't hold it. I found an old video online that showed the needle bar and it looks just like the attached pic of mine, where there's a slot extending well past the clamp. Eventually I set the left needle flush with the right needle and it now sews the seam shown. Setting it up higher (as I thought sergers were supposed to be), it won't pick up the needle thread.

Does anyone have any insight about what's going on? I'm going to keep scouring the internet in the meantime.

Thanks!