CB4500 reverse stitch bottom loops

[Zandeosaddles]

Good day all. I am having a problem with my machine. It stitches fine forward, but in reverse it makes loops underneath. I have run through all the instructional videos on you tube. All the basic checks are done. When in reverse, the machine sounds as if the tension of the upper thread is too tight as opposed to sewing forward, yet it is the top thread that loops underneath in reverse. I would greatly appreciate it if someone would take up the challenge of running through all the settings with me esp the uncommon ones. My machine was never properly setup by the agents in south africa. I got a technician out to set it up. I recently re did the timing, feet balance threading, oiling race screw tension from videos, just to be sure. The thread is wound correctly on bobbin.  my email address is zandeo@gmail.com. thanks very much.

[CowboyBob]

Looping is almost always upper tension.Double check that you have the thread wrapped around the second tension 1&1/2x.

It's looping because the upper thread tension is too loose.

[Uwe]

I'd open the hook cover, turn a few stitches very slowly in reverse by hand and closely inspect what's happening as the thread gets wrapped around the hook. Your top thread may snag some place in reverse and pull more thread from the spool, which the take-up lever cannot pull tight anymore. A video snippet uploaded to Youtube is a great tool for remote debugging. 

Edited May 26, 2017 by Uwe

[Uwe]

So I was just trying this out on my Cowboy 4500, and, lo and behold, it does the exact same thing when I reverse at maximum stitch length! It sews just fine in both directions when I select a smaller stitch length, but at maximum stitch length in reverse, the thread loop snags momentarily between the shuttle and race, the take-up lever pulls more thread from the spool with a snapping sound in the upper thread path, and leaving a loop at the bottom.  I'm not sure yet why the thread snags or how to fix this, actually. I guess it's my turn to take a video snippet of my machine misbehaving and report back.

Edited May 26, 2017 by Uwe

[Uwe]

The fix was super easy!  Just point a camera at the machine and threaten it with public shaming in social media and it'll make perfect stitches in both directions at all stitch lengths! 

Edited May 26, 2017 by Uwe

[Hockeymender]

59 minutes ago, Uwe said:

The fix was super easy!  Just point a camera at the machine and threaten it with public shaming in social media and it'll make perfect stitches in both directions at all stitch lengths! 

So now you tell me.....after all those hours working and sweating over these misbehaving machines!!

[Uwe]

I finally got a few snippets of film catching the machine as the thread gets snagged. It's hard to see and even harder to film, but my machine actually manages to snag thread in two different ways. One is subtle and only causes somewhat loose stitches at the bottom, the other is a major snag and causes big loops of top thread on the underside.

The main problem is when the thread gets snagged between the shuttle and the race: 

 

The photo below shows four rows:

Top: forward

Second: reverse with big snag loops

Third and fourth rows are forward again with smaller stitch length followed by reverse with moderately loose bottom stitches.

 

I still don't know exactly what causes the snags or how to fix them. 

I put together a few video snippets showing how my machine catches the thread under certain circumstances. This is not some elaborate how-to-fix-it video, just documenting what can go wrong. 

 

 

[LumpenDoodle2]

Have you tried switching it on and off again?    Sorry, couldn't resist, that's my 'fallback' repair position'.    

Just out of interest though, is all this only happening at a specific point of the stitch cycle.   If reverse is chosen when the needle is slightly higher/lower, does it make it worse, or cure it.  

(I meant to use the word excasserbate, but neither me nor spellcheck could cope).

 

[gigi]

Just an opinion: Hook might be a little bit behind, timing-wise.

 

[Constabulary]

Is it probably the shuttle race spacer where the thread keeps hanging? Aren´t there different size shuttle race spacers out there? At least the 441 parts list shows a range of spacers in the listing.

Idea is when you add a thinner spacer (don´t know in what thickness they come)  the hook goes in a bit deeper and then there is a bit more clearance between "shuttle driver tip" and shuttle so the thread can easier pass through. Just a a wild guess guess

Or try thinner thread and check it it still does the same thing...

Have attached a 441 type parts list where the spacers are listed (#44 -#50)

part-441.pdf

Edited May 27, 2017 by Constabulary