With just a little patience and a few dollars in parts, any garage builder can make or modify an existing cable to the proper length, preventing the problems that come with poorly routed cables and too much or too little slack. I usually use a special tool I made for crimping the cable housing ends, but in this demo, I'm going to use a really simple tool I made when I very first started fixing bikes.
Nothing in this post is especially expensive, and the only thing that really can't be found locally are the cable parts themselves, however, the cable ends, sheathing, sheathing ends and cable itself can be purchased online through motion pro's website. If you're shortening an existing cable, you really only need purchase the housing end, and the cable end.
The first step is to establish the length of the housing, then cut it to length and clean up the ends, I like to use a drill bit to pick out the scraps of the nylon sheath that like to get stuck inside when you cut it. Then pop on the ends, and using a really simple tool, you can stake the end to the housing so it'll never come off.
Then establish the length of the cable itself, if there are any adjusters in the line, I like to move those to fully tight and make the cable a touch on the long side. The ends for the cable can be purchased online, or can be made with a drill press and file, I make mine from brass on the lathe, but if I did a lot of cables I'd certainly buy a cable end assortment.
I keep some silver solder in my solder pot, which is just a scrap stainless part with a cap welded to the end, I find that if you don't have any tools to make something like this, a stainless measuring cup works just fine! Some plumbing flux and a blowtorch are the only other tools you'll need. Just put the ends on the cable, flux it, smoosh the end of the wire so it frays and won't easily slip back through, and dip in the hot solder pot. The flux, if done right, wicks the solder all the way through and around the cable end, ensuring a really good solid bond.
After some cleanup on the grinder, or with a hand file, the cable is ready to go, no more shotty cables on your cafe racer!