Constabulary

I doubt it will be an upgrade. Why do you think it could be an upgrade? If the Consew has a larger bobbin that IMO would be the only improvement. Both are Chinese made clones of the Singer 29K with minor downgrades from the last Singer version 29K7X

if you cant find one used check with CL Machinenbau - they still make the shuttles for the 8346-20 https://www.cl-maschinenbau.com/de/leistungen/naehmaschinen.html But do not expect them to be cheap 😉

just checked the parts list - it should be screw 91-100 331-15

IIRC the 491 is using a leaf spring for the foot pressure (similar to Singer 111w - kind of) so there should be a screw on top of the machine at about in the middle of the top arm.

you have to pull out the foot bar. You have to loosen / remove theses 3 screws too - see rec circel. Alos make sure you removed the return spring that pulls back the presser foot (not meaning foot pressure spring)

to me it looks like a Juki 555 fabric / tailoring machine of some kind

you probaly have chosen a short stitch lenght or the bell crank lever is worn down (or both). Maybe teeth on the presser foot are dull / worn down. Also theck if the "gib" on the stitch lenght adjuster is installed correctly. See pictures here:

Hope this helps 😉

Looking at this picture I belive the Singer 107w hinges are the same. https://www.college-sewing.co.uk/202258-210844-machine-hinge-hook-singer-107w.html?srsltid=AfmBOopJb1ilppAZoElRixRJKheoNF9ftFELvIPI6Cw_MaVvn7w75taq https://armastore.eu/210844-singer-107w-hinge-hook You will get them on your end as well just check the numbers online But I would probably buy the female part too - you never know....

Looks like the shuttle race is not installed correctly,

in addition to my last post: Just in case you think the 29K71 (or other patcher machine - no matter the brand) is a great heavy duty leather sewing machine ... it clearly is NOT! Its is a machine for repair work but not for producing leather goods. It may work for odds and ends in your privat environment but not for pro leather work or for producing goods you probably want so sell. I´m barely using mine but if you need it for "odd work" then it is indispemnseable - it can do work that other machines can´t do.

I have sewn close to 12mm webbing with mine. But thats not what it should sew every day. I just played with some parts setting, no other chnages no grinding or welding or so. And stitches become shorter the thicker the material is.

A Singer 144w as it seems. More or less the "fat brother" of the Siger 111w.

depends on what leather product you want to sew with what needle / thread size. By design it is a high speed tailoring machine and not really a leather sewing machine. It would not be my 1st or 2nd or 3rd... choise.

I´d check the needle - hook timing / needle bar height. My guess is the NB is set a little to high.

I´d try this by hand cranking the machine but again the needle hole has to be wide enough for 2 thread strands + needle. 214x1 / 328 needles have the same dimensions as 216x1 and I´m using the 214x1 in my machine w/o problems. 216x1 has a slightly different needle tip they have some kind of channel in the tip - not sure why. In case the hook tip hits the needle you have to move the hook a bit to the right and probably the bushing of hook driving shaft too. But it depends on how the machine is set up. Back in 2015 when set up my long gone 133K I started this topic:

why is the bottom thread under the latch of the bobbin case? Always good to read the manual fully (no offense) - I guess you have a manual, right?

The resistance probably is when the foot lifts up cause it then is working against the foot pressure spring. The higher the foot lift is set and the higher the foot pressure is the more resistance you feel. Just my thoughts. I´m not in front of the machine.

is it just me or does the cam track look concave? It should not look like that, right?

basically it depends on the size of the needle hole in the needle plate. I never tried to max out what it can sew but 207 / 277 thread with # 24 /25 needle is not a problem with mine.

You can use other needles systems but you have to adjust the needle bar height. I´d be glad if I could find a 97 on my side of the pond. 😁

https://www.ebay.com/itm/157174686380 Not mine (obviously) but could be interesting for some folks in the US. Ex factory it is a straight stitch and cam controlled 3-step 8mm wide ZZ machine (subclass 135). It shares presser feet, feed dogs, needle plates and probably some other parts with its "older sisters" like 107w, 143w and the like. Found it as I´m about repairing one and looked for information cause I have one here that needs a new cam. 🤥

If it was me I´d check with a professional leather cleaning / restoration service. DIY like "vinegaroon'ing" may work but it could get worse also. Again, I´d check with a Co. who is restoring / reconditioning leather. If you have one locally they may come to your house and check the damage. May cost some $ but a new leather couch most likely is more expensive. Not on my end of the world but these folks f.i. offer telephone support: https://clydesleathercompany.com/pages/about-us

Needles should be system 88. Not sure which manual you have but this one (German Language) should be fairly close: Claes+Elastik+I+u+III_cleaned.pdf

just figured I could be wrong with that - just found this thread regarding a 105-27 and it seems to have screws in this subclass. 😉