Juki 341 issue

[the deacon]

Hi all,

An issue has cropped up with my 341 and I can't figure it out. It kind of appeared after a month of down time for the machine. Thought it might be a lubrication issue, so I oiled all points to no effect. I don't see the needle striking anything. The seize up seems to happen on the up stroke of the needle, I can "push" through it if I turn the belt pulley.

Any thoughts?

Thanks.

 

[Wizcrafts]

Can you remove the feed dog shaft and see if that frees the action? If so, the clearances have changed due to the weather and the shuttle is hitting the feed dog mounting bracket. It could be either the feed dog bracket and its mounting bar on the bottom, ot the shuttle drive gear or its shaft position under the arm. Those shafts are positioned and tensioned by tapered screws on the ends.

These are not definitive statements. The binding could be internal. It might be weather related, or even due to a loose, backing out screw on a rotating part.

[Uwe]

You need to find out exactly why and where it binds. "Pushing through" on motor power is almost never a good thing on a sewing machine. Disconnect the motor and turn it by hand. It's only way to really feel the bind and debug it. 

I had one 341 class machine that had a set screw on the hook driving cone gear touching the opposing cone gear. Took me hours to figure out. 

[Wizcrafts]

3 minutes ago, Uwe said:

You need to find out exactly why and where it binds. "Pushing through" on motor power is almost never a good thing on a sewing machine. Disconnect the motor and turn it by hand. It's only way to really feel the bind and debug it. 

I had one 341 class machine that had a set screw on the hook driving cone gear touching the opposing cone gear. Took me hours to figure out. 

Exactly what I was thinking at the end of my suggestions. This actually happens more often than we anticipate.

[the deacon]

Thanks Wiz and Uwe,

Just to clarify, I never pushed through on motor power, (actually the motor couldn't push through). I manually turned with the wheel.

I'll pursue your recommendations and let you know what I find!

 

[Wizcrafts]

If you don't find any protruding set screws and the shuttle isn't hitting the feed dog bracket, check for some thread fragments that might be jammed in or under the bobbin basket. Also check for mice under the machine.

[Constabulary]

The first thing I would do is put back on the throat plate and make sure it is correctly installed and then make a Video again. Running the machine w/o throat plate the as you show in the Video will probably cause a binding when the "uncontrolled" bobbin case hits the bobbin case opener.

Make sure the little tab on the bobbin case sits inside the notch of the throat plate and then try again.

 

 

Edited January 10, 2018 by Constabulary

[the deacon]

Constabulary, the exact issue was present with the throat plate attached, i removed for the video it in case it was easier to see and diagnose.

With the feed dog shaft removed the issue persists.

Sadly I don't know what the hook driving cone gear looks like. Does anyone know where to find a parts diagram for this machine? The owners manual doesn't give good diagrams.

[Constabulary]

are you sure the tab was in side the notch? if not try it. Other than that I would also think it a set screw that blocks the hook. Seems gear #48 is not attached with set screws so check set screws #57.

EDIT:

You can downlaod the parts lits here:

Parts List Juki 341

Edited January 10, 2018 by Constabulary

[the deacon]

Thanks Constabulary.

Just looked and the set screws are well set. I did take out the bobbin basket and it caused the binding to go away. So must be something with the bobbin. Could it have been a bobbin case opening lever adjustment issue? Is there a good resource on how to dial it in?

 

[Constabulary]

As I said before - reinstall all parts and make sure the small tab of the bobbin case is inside the notch (not left or right of it) and then check again because thats how we can se if something is binding under regular sewing conditions.

[Darren Brosowski]

My first suggestion was going to be the basket as it only takes a microscopic amount of thread or rubbish to cause binding.

Pull it back out and look very closely at the male and female slots to see if something is in there. If it is damaged in any way I would replace rather than try to polish out

[the deacon]

reinstalled and there is no more binding. I have no idea why it is working now. Perhaps I didn't notice if the bobbin case was not inside the notch when I first took it apart. One question. I notice that my bobbin opening lever has an ever so slight bit of play and a distinct clicking sound when wobbled. Should that be?

 

thanks for all the help!

Edited January 10, 2018 by the deacon

[the deacon]

scratch that. After test sewing it's still happening, though intermittently. Ahh the joys of machine maintenance.

 

[brmax]

What is the noticeable difference when oil is applied to the basket, in typical amount. I am curious if some grit has made a bur in the raceway. Best to have the throat plate back on while checking this. 

Good day

Floyd

[the deacon]

I applied some oil when I re installed the basket. This may have accounted for the machine to be working a bit better than before. I did run my thumb nail around the chase and basket. I didn't feel any burrs. I suppose I could order a new one and see if that solves the problem.

I've never adjusted/set the timing on the machine. I'm wondering if that could be the issue?

[Uwe]

This binding trouble may have to do with the bobbin case opener in two totally different ways.

1. When the throat plate is removed like in your first video, the bobbin case rotates more than it normally does and the bobbin case opener finger pushes against the triangular bobbin case tab and causes a bind. You can see the bobbin case popping backwards when the bind releases.

2. When the throat plate is installed, your bobbin case may simply be pulled back too much, causing the tab inside the throat plate cutout to touch and cause a bind. Neither of the videos shows that detail to verify or disprove.

I made a video that hopefully will illustrate what I was trying to say in words above:

 

Edited January 13, 2018 by Uwe

[Constabulary]

Not possible to explain this any better - again great video , Uwe  

This works for any sewing machine rotating hook who have a bobbin case opener similar to the one shown in the video not just Juki 341 (Pfaff, Singer, Consew, Seiko, Adler... you name it) so it´s worth watching.

 

[the deacon]

Uwe,

Exceptionally helpful video, Danke Uwe. The bobbin case timing was off. I have adjusted and have much better results. I noticed on your video the loop that is created by the hook is much tighter than mine which seems to me would cause less efficient stitch execution and/or sloppier stitches (first video). Is there an adjustment to make to tighten that up. Also I noticed there is a little bit of play with the finger that pulls back the bobbin switch, there is also an audible click when moved (second video). Is that normal or is this part loose in some way.

Again, thanks so much for a great video tutorial.

Dieter

 

[Wizcrafts]

You can loosen and tighten up the loop by readjusting the position of the check spring disks. Loosen the small screw near the top of the disks, which sits inside a curved slot. Use your fingers to turn the disks one way or the other until you get the amount of slack you are happy with. Then tighten down the set screw.

[the deacon]

Thanks Wiz. I made those adjustments, I didn't see too much change in loop tension. I also moved the spring stop per Uwe's video on adjusting the check spring tension. I think it's pretty good. I have to do some more thorough sewing to be fully sure. I did see another issue while doing all this. It has to do with the feed dog. I'll start another post so as not muddy up the valuable info here.

[the deacon]

One more thing. I noticed there was some play and an audible click with the finger that pulls back the bobbin switch.

Are those normal tolerances?

 

[Uwe]

On my Juki LS-341 that bobbin case opening finger is rock solid, has no noticeable play and makes no clicking sound when pushed. Perhaps something didn't go back together quite the right way after you removed the hook.

I'm also a little surprised that we have totally different hooks in our supposedly identical machines.

Edited January 20, 2018 by Uwe

[brmax]

From this last part of the discussion, I am going to assume there is some slack. This end play/slack is up and down. Its where the inner hook guide/bobbin case opening lever Plate sits in my oppinion.

From looking in the 13 series parts book, this is showing a couple different hooks. Interesting hook differences and case “ hold down part”. But anyway I think importantly here in this discussion is, that the case opening lever is on a plate assembly. This is like my 1341 So keeps my interest. Also like my own a slight bit of end play or slack, this will enable the lever to move. Actually still end play, though when pushed as mentioned earlier it actually tilts ( noise/click ) the plate. This seems to move and so can be an adjustment to use some Kentucky windage when adjusting. In this I suggest adjusting to a bit more slack opening. 

Im hinestly going to be glad in understanding better how best to remove the end play. This may be accomplished with the different but available shims on the gear side but I’m not sure with this plate assembly.

On a bit more with hook differences, I see the 1340 and 1341 differences, I suspect not much different than the 340 & 341, I do recall this different bobbin style from a long time ago ( and liked it ) but I have the cap style, maybe adler style of a sort. 

Have a good day there

Floyd

 

ps: respectfully to Juki mine was this way out of the box. I work with it!

Edited January 20, 2018 by brmax