TOPIC:

Sure they will stretch.. Just yank that right hand side thingie full whack about 1,324,857 times?

In other words, Not for a second 

Found some old pics with OEM cables, and they too were a tad short. 

I'll reply to Zed-Parts, but I doubt they will change the length.

 

"........some of the carb kits are awful. We have compared them to the ones we sell and you can see why carbs do not work when fitted with these. They go for around £12 whereas ours are £58."

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I've used the kits noted below, for Years!  Never had any Tuning or Running issues ! 
Ebay.    (can't get the link to work)
"3 Pack KZ1300 KZ 1300 Carb Carburetor Rebuild Repair Kits Sets Jet Set"

Currently using these on the carb.-set that's getting 58mpg @ 60mph. 
 
 I do however ensure 2 things with these kits.
1) Check that the float-needle retaining spring is not in conflict.
(This may have been corrected because with the last 2 kits the spring retainers were OK).
2)  I purchased better quality C-clips for the  main-needles and the choke-plungers.  The ones supplied are garbage !
 

OEM - 72 mm - top cable
Zed Parts - 60 mm

Tried running cables with both nuts at thread end, but the geometry presented a noticeable stiction point right off idle when opening throttle. Sticky.
 

As I told you in the first post.
You must cut the cable sheath one centimeter.
Separate the cable sheath a few centimeters from the tensioner screw and cut it with pliers, being careful not to damage the cable.
You will have a wider fit tolerance.

Yes, that would work, Thank You.

But since the cables do have slack, I'd rather not attempt surgery when surgery may end up nicking the cable. And, the cable must be glued to the ferrule, as the two pieces don't want to easily separate.

After the cable 'beds in' I'm sure it will fit purrrfectly! <sarcasm> to Zed-Parts response..