Juki 341 Lift Height Adjustment

[friquant]

When I adjust the overall lift height using the banana slide (A), do I also need to set the needle point flush with the throat plate and then momentarily loosen the bolt (B) in order to restore equal lift between the walking foot vs the presser foot?

Somehow I assumed the banana slide (A) was all that was required to increase/decrease overall lift, but if I only adjust at the banana slide then afterward one foot lifts much higher than the other.

This is on a clone of a Juki 341. 

Edited June 20 by friquant
clarity

[kgg]

11 hours ago, friquant said:

When I adjust the overall lift height using the banana slide (A), do I also need to set the needle point flush with the throat plate and then momentarily loosen the bolt (B) in order to restore equal lift between the walking foot vs the presser foot?

Here is a copy of the Juki LS-431 engineering manual refer to section 9 page 12.

kgg

[Northmount]

5 hours ago, kgg said:

Here is a copy of the Juki LS-431 engineering manual refer to section 9 page 12.

kgg

Copy not attached

[kgg]

15 minutes ago, Northmount said:

Copy not attached

 

16 hours ago, friquant said:

This is on a clone of a Juki 341. 

Sorry, early morning Nicotine level was low. Hadn't had my second cup of coffee and enough vaping. Use to be second cup of coffee and six smokes.  

kgg

341 engineer manual.pdf

[friquant]

Thanks for replying. Sorry I should have given more background. The engineer's manual for the Juki 341N (attaching photo of page 12) shows two separate adjustments:

1. Overall lift height
2. Balancing the lift between the two pressers

The manual does not explicitly say If you adjust #1 then you will afterward need to adjust #2, otherwise your feed timing will be off and your lift heights will be unbalanced. But I wonder if maybe that is what is required...

The first few times that I adjusted the overall height (1) based on the manual I was baffled that lift height was unbalanced afterwards, or that feed timing was off afterwards. Eventually I tried doing (1) then (2) in succession, and that seemed to give a good effect. But it also got me wondering if it's typical to require (1) then (2) in succession, or if there's something else out of adjustment just on my machine that makes it require this two-part adjustment.

 

[friquant]

Here are some additional photos and measurements that may show what's going on.

Before taking these photos, I verified that the the top feed cam timing was correct based on pp 15 of the Juki 1341 engineer's manual.

Then I set the needle even with the throat plate, and took these pictures first with the hinge bolt at the bottom of the banana slide, and then with the hinge bolt at to top of the banana slide.

I conjecture that the design length of the top feed cam rod, combined with the radius of the arc in the banana slide are supposed to be such that sliding the hinge bolt from one end of the banana slide to the other does not actually move  the upper feed driving shaft. (Assuming correct top feed cam timing, and assuming both presser feet are against the throat plate.) 

But on this machine, it DOES move the upper feed driving shaft. That is, starting at the first photo (both presser feet against the throat plate, and needle at the throat plate, and verified balanced lift height) then sliding the hinge bolt to where is shown in the second photo, the upper feed driving shaft moves away from the main shaft, lifting the vibrating presser off of the throat plate by 5mm.

BTW this is a Jiang Long 341, which is a clone of Juki 341N.