Seems I broke my Juki-LS-341, again... (Bobbin Shuttle)

[Yoshi888]

Finally had some time to properly check and fix everything.
I first readjusted the gear on the horizontal axis, but that did not seem to make too much of a difference.

Next, I checked where the play on the horizontal axis came from. So I removed the Belt cover and opened everything up.
I found that the bushing that keeps the axis in place (as shown in the screenshot) had come loose.
Resetting that part removed all the play in the axis and also stopped my machine from locking up!

So it seems I have found the culprit and fixed it!
The only remaining problem seems to be that while doing all that, I have changed my needle timing after all...
As seen in the video below. It seems in the end I will also have to learn how to adjust the needle timing.

At least once I learned that as well, I am confident I probably will not need a mechanic for my machine anytime in the near future, which is good as the next one is more than 200 km 😂

@AlZilla @friquantThank you so much for the help, I appreciate it a lot.
Do you also have any tips or resources for setting the needle timing :)?

Kind Regards 
Josh

[friquant]

Nice work finding the offending bushing! 💥

Here are a couple of excellent videos by Uwe on the general practice of setting timing:

https://www.youtube.com/watch?v=1wNBPX8i524
- video by Uwe of Consew 225

https://www.youtube.com/watch?v=pL9WiZeKZAY
- video by Uwe of Adler 67

Since these videos are conducted on a different machine, what you actually loosen and adjust will differ but the overall principle is the same.

Your juki user manual will have factory specs for needle bar rise, needle bar height, and hook to needle distance. These will be adequate to get you sewing again. After you become a pro at timing by the book, you might also enjoy How to Stuff a Hook and New Way to Measure Timing. 

[AlZilla]

I'm not familiar with that particular machine but the basic process is to roll the machine over until the needle rises about a quarter inch or 3/8" back up from the bottom. Then find whatever you need to loosen the shuttle hook so you can rotate it. Set the point of the hook right above the eye of the needle, exactly in line with the needle.. The exact measurements will probably vary for your specific machine but should be close enough to stitch.

The hook should all but touch the needle. There a spec and a way to adjust it if needed.  Also, if the point of the hook doesn't align right above the eye of the needle, you may have a needle bar height adjustment to make.

For me, the big thing is to remove things like needle plates and food dogs so I have a good, clear view.

Do it a couple times and you can do it in your sleep.

[Yoshi888]

Thank you very much @friquant for the videos. They were very helpful. I had been wondering how I get these measurements right and the tips from the video were extremely useful! 

I have also found the needed measurements from mine in the Manual.

But alas it seems theres one problem left. 

I have prepared everything and removed the screws (4,8) as instructed. But the gear on the horizontal shaft does not move or rotate an inch. 

I understood from the manual that after loosening the screws I could retract it to disengage with the wheel on the vertical shaft, allowing me to adjust the hook in the proper position before engaging and fixing the gear in place again. But I absolutely can't get it to move and didn't want to use more force in case I misunderstood how this steps works.

 

Did I misunderstand the process or is the gear just very stuck?

 

Kind regards 

Josh 😇

[AlZilla]

3 hours ago, Yoshi888 said:

I have prepared everything and removed the screws (4,8) as instructed. But the gear on the horizontal shaft does not move or rotate an inch. 

Seems like it ought to turn. Heat from a hair dryer or heat gun and/or I'd take one or more of those screws all the way out and put some kind of penetrating oil in there.

[friquant]

On 10/29/2025 at 5:15 PM, Yoshi888 said:

I have prepared everything and removed the screws (4,8) as instructed

There are three set screws to loosen. How many did you loosen?

Once all three are loosened, if still not moving you can add a few drops of diesel and let it sit to dissolve some of the corrosion, if that's the issue. You can also screw one of the set screws partway out, then place an end wrench (or spanner wrench) around the gear, using the protruding part of the set screw for the wrench to grab onto. (Go gently though)

[friquant]

On 10/13/2025 at 3:56 PM, Yoshi888 said:

Once I collect my nerves this week, I'll try to reset the horizontal shaft and fix it in place again.
Hopefully, if I watch out for the correct position, I can also save my hook/needle timing.

If you cannot get the gear to move, you could loosen the shaft again, and move it over the right number of teeth to bring your timing back to what you had before.

[Yoshi888]

I have now managed to do the needle-hook timing. While the gear on the horizontal shaft was indeed very stuck, what worked for me was to insert the hex key and turn the shaft, and with enough leverage, I was able to turn the gear on the shaft to adjust the needle-hook timing.
Additionally, I saw that I also had to adjust the position of the tip of the hook as it was hitting the needle slightly. This is where I made one mistake as I first loosened the screw for the Inner Hook Guide instead of the hook driving shaft saddle. 

So after I finished the Hook-Needle Timing, I wanted to adjust the position of the Inner Hook Guide again , but no matter how close I set it, it releases the bottom thread way too early (I once again attached another video)

So did I do something wrong with the hook-needle timing? I had to adjust it further than I would have originally thought. So, did I maybe miss something in regards to the stitch cycle in which the parts work together? I tried to look at some other resources, but could not spot an issue or difference.

I really tried all options with the possible positioning of the Inner Hook Guide, so I don't think it could be just that.
So once again, I hope you have some ideas or help.

But I really think this should be the last step. At least after this whole ordeal, I feel much more confident regarding any issues my sewing machine might throw at me in the future 😂

 

 

Kind Regards 
Josh

[friquant]

13 hours ago, Yoshi888 said:

I first loosened the screw for the Inner Hook Guide

Can you post a picture of the inner hook guide? I'm not familiar with this term.