Class 26 Loose Stitches/Loud Noise

[LiftPig]

Here's my (I think) resolution post for my own reference and for anyone else running into problems who don't want to go through all the posts above and just want to skip to the weenie.

I ran several pieces yesterday with 138 on a #23 needle through 8 ounces of veg tan married to 4 ounces of soft oil tan with contact cement and got good stitches and a quiet machine.

1.  I shortened the throw of the check spring by loosening the screw on the underside of the device and moving the curved piece of metal clockwise about 20 degrees.  The video from @Uwe posted above explains the proper position.  The screw isn't obvious, it's not the two screws on the front of the disk, it's the one on the bottom going through a curved slot in a piece of metal that looks like it can be adjusted - you'll need to get your eye level below the disk and look upwards. This gave the top thread more slack coming around the bobbin case so it follows the contour of the case smoothly and at an even rate. The video for that is a couple posts above.

2.  I adjusted the bobbin case opener to allow just enough room for 207 to pass through without binding up and no feeling of binding on the machine when sewing.  The video on how to do this is below.  Make sure when you think you've got it you turn the hand wheel slowly and feel if it is a smooth travel all the way around.  If it feels like it's binding, you're probably adjusted too tight and you need to back that adjustment off a little more so the bobbin case opener isn't straining as the machine works.

3.  I retimed my machine so that I'm advanced of the recommended 1/8" above BDC for my timing moment.  I tried setting my timing so that the tip of the hook was at 12 o'clock when the arm was at it's very top and ended up skipping stitches.  I backed to about 11:00 and that seems to be the sweet spot for my machine.  I'm not sure where that relates to the needle above BDC because I didn't take the feed dogs off to measure precisely. It's around 3/16"-7/32".  That video is below as well with the following disclaimer:  Uwe mentions adjusting the timing belt.  He has since posted that was the incorrect adjustment and was not the correct solution.  The correct adjustment is the hook timing.  Don't mess with the timing belt.

 

A couple tips:

1.  The Class 26 is a Juki 341 clone.  There's a paucity of videos and info about the 26 but a bunch of stuff about 341 and Tacsew 1563.  As best as I can tell they're identical in all the ways that matter.

2.  Start with adjusting your hook timing.  I did this backwards and started with the check spring adjustments, then the bobbin case opener, then the hook timing.  Go in the opposite order.  In my case the hook timing was the big winner, though the other two needed a bit of refinement too.

3.  There's a second component to the hook timing, and that's the needle bar.  It's mentioned in the video by @VanPlew above.  If your timing is thrown off because you hit a snap or something, you'll probably need to adjust this too. 

4.  The manual that came with the Class 26 is pretty bad.  A couple posts above @Tequila shared some much better manuals.  Go download them.  

 

Thank you!!! to @Wizcrafts, @kgg, @Burkhardt & @Tequila for their help and to @Uwe for taking the time to create videos that we can all watch and learn from.  

 

Bobbin Case Opener Adjustment

 

Timing Adjustment:

Please note, Uwe mentions adjusting the timing belt.  He has since posted that was the incorrect adjustment and was not the correct solution.  The correct adjustment is the hook timing.  Don't mess with the timing belt.

 

[TomE]

Thanks for the summary. Good info that will help me navigate future (inevitable) challenges. 

[Tequila]

@LiftPig it’s too bad that you had all those problems, but on the bright side you now know that machine well and if something ever comes up again you’ll be confident you can fix it. Thanks for the videos and keeping us up to date.