I've got VM's too. I used my stock throttle cable by modifying it, but the process should be about the same.
1. Before cutting anything mock up the cable location routing it along the frame or wherever ur going to leave it. Id have the carbs on the bike so u can account for the actual mounting point. You want a slow curve to the top of the carbs, so the cables don't bind out.
2. Cut the cable outer cover to length, but over estimate, and cut more off as you go.
3. Fix the throttle end first, make sure you have enough naked cable to be able to go from idle to WOT.(I didn't have to do this end of my cable, so id seek out further help on this subject)
4. Unscrew the tops of the run the cable through the top, the retainer (the 3/4 metal circle inside the top of the slide, and through the slide. Don't run it thorugh the spring, we're still figuring lenght at this point.
5. On the bottom of the slide I used a lead bb weight for mocking up the correct cable length. When clamping the weight on only make it snug, dont crimp ur cable. Push the slide all the way down to it and put the retainer in place.
6. Drop the slide into the carb and screw the top all the way back on.
7. Keep adjusting the placement of the weight until when the slide is all the way down with no slack in the cable. Make sure the slide is ALL THE WAY DOWN.
8. Mark the cable at the top of the weight. Take the weight off, and remove the top of the carb and the cable. Run the cable back through the top of the carb, the spring, the retainer, and the slide. Either get someone to help you hold all these parts up the cable and our of the way, or use a vice grip to slightly clamp on to the cable.
9. Crimp on the ends, and solder them, only if you are sure they are in the right place.
I'll try to run by the garage today and take some pics. Hope this helps.