Norman has a video but i can't find it now.
what i did, was;
before you cut anything, measure how long the cable is from the throttle nub to the housing. you need to get this close, or you won't be able to adjust it properly.
next, cut the cable and the housing down to the size you want. put the cable back in the housing before you make the end, or else it won't fit back in.
to make the end, take a strand of the cut off cable and wrap it around where you want the new nub to be. wrap it as tight as you can, and you just need a piece a little smaller than the nub.
now, you need silver solder (regular solder won't work,) flux, and a torch.
dip the cable in the flux, fire it up with the torch, and solder over your wrapped end.
when you've got a nice little ball, dip it in some water, then pull on it as hard as you can to make sure it ain't coming off. if it fails, it's falling into your carb and into your motor. then it's all over for you.
grind or file away some if it's too big, then reassemble.