Clean the thread path under the bobbin case spring
It's unreal how much crap collects under here:
Step 1: Rotate the Bobbin Case until you see both of the two tiny screws
[ATTACH=CONFIG]371142[/ATTACH]
Step 2: Turn the right screw until it's fully seated. Make note of how many turns it is until it's fully seated. This is your tension adjustment. Counting the turns will let you set it to the same setting as it was before you did this cleaning.
[ATTACH=CONFIG]371143[/ATTACH]
Step 3: Remove both screws carefully, they're tiny, and they jump! Put them aside for now. The spring will probably fall off, just set it aside with the two screws. Clean the path where the thread goes.
[ATTACH=CONFIG]371144[/ATTACH]
Step 4: Replace the spring, and make sure the curled end is tucked into the hole.
[ATTACH=CONFIG]371145[/ATTACH]
Step 5: I like to tighten the left screw about half way before I install the right screw.
[ATTACH=CONFIG]371146[/ATTACH]
Step 6: Install the Right screw, and tighten then loosen it to the setting you recorded above. Don't forget to fully tighten the left screw when you're finished.
[ATTACH=CONFIG]371147[/ATTACH]
Step 7: Now you're finished!! Time to test sew!
[ATTACH=CONFIG]371148[/ATTACH]
If you find that the lower tension isn't what it was, adjust that right screw. Turn it clockwise if it's a little too loose. A little counter clockwise if it's a little too tight. Make tiny adjustments, 1/8 turn at a time. Test sew after each adjustment.
And a picture of your model for this particular tutorial. She's all ready to be stripped and repainted:
[ATTACH=CONFIG]371149[/ATTACH]