Replace Gear Stack Cam on Bernina 730

eBay in Australia and Canada. Are you sure it is broken? There seem to be issues, 2nd link

BERNINA ARTISTA 200, 730 TOUCH SCREEN ' eBay

https://www.ebay.com > ... > Sewing Machines & Sergers

This is a replacement LCD Touchscreen Suiteable BERNINA ARTISTA 200, ARTISTA 730. If your sewing machine is experiencing the problems below, then our ...

https://www.google.com/search?q=touch+screen+bernina+730+artista

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Try;

Bernina Store & Sew Much More
7081 West Boulevard
Boardman, OH 44512
P: (330) 726-9396
Email:
[email protected]

This series are prone to cracking the cam gear. Search Bernina cam gear at www.ashleyandthenoisemakers.com and there is a full example with pictures on how to do it. Try ebay for the gear. Check prices.

I don't know what a stitch cog is by your definition but I suspect that you may be referring to the cam stack worm gear, part # 310 007 03. These gears are available, however those produced and sold as after market parts online have ranged from bad to very bad. I would suggest that you find an OEM part (not a reproduction) that are still available from time to time on EBAY etc.
Changing the gear is not as straight forward as it may look. The proper replacement requires: 1. removal of the cam stack without damaging the machine parts, 2. removal and installation of the new gear with the correct alignment of the individual cams, 3. installation of the cam stack and pattern indicator without axial play, 4. correct parabola timing of the main-shaft worm wheel and cam stack gear, 5. synchronization of the zigzag and automatic cam parabolas, 6. pattern indicator timing, 7. checking and adjusting the automatic needle position. SewTechnical Home

try changing the needle--one for the fabric being sewed
also the zig zag could have a worn or damaged gear or cam
or there could be a timing problem.

It does not matter where the position of the camstack is when you put it in, it should not affect any other part of the machine.

Should not make any difference, put the camstack in, there should not be any timing marks and it should not affect the machine

Typically, ther are two problems with locked up Bernina 730's:
1. Look for a split in the worm gear on the cam stack...(white Delrin systhetic gear attached to the steel cams.
2. Look for a crack in the vertical shaft gear...(Delrin synthetic gear as well)
These gears have given great performance for over 40 years and may need to be replaced...

Check to see if the cam stack gear does not have a crack in it. The other problem is the cam engager lever is does not engage the cam stitches because it is gummy. To solve this, lift the lid and follow the lever to where it make contact, add a penetrant oil. More the lever back and forth as fast as you can and work the penetrating oil into the area. It should click back and forth and snap between the back and front V's. One is for the zig zag and straight stitches and the other is for all cam patterns. Once it is clicking and snapping back add regular oil. Thensew out your pattern stitches. If the machine binds then you could have a cracked cam stack gear and has to be change by a Bernina service center.
SewTechnologist