Loopy Loops

[theeverygirl.livejournal.com]

Hey crafty grrls and guys:

I'm trying to sew rubber, bicycle inner tubes specifically. I only need to sew through two layers. I am using a teflon versatile foot. The stitching looks fine on the top but is loopy on the bobbin side, so I can just pull the thread out (top thread and bobbin aren't locking). Sometimes it just skips the stitches entirely. I tried:

1. Changing the top thread tension.
2. Taking apart the bobbin area, brushing out lint, and lubricating. This made the stitching work properly for about 2 seconds.
3. Changing the presser foot tension.
4. Using heavier thread.

Nothing seems to work; still loopy. Any suggestions? The only thing I can think of is using waxed thread.