Make sure you got the right cable. The end that goes into the tranie is a round shaft (think finishing nail) with a small tab that sticks out of one side. Some other brands have the shaft with a slot running up it. Still others have the little square end to the cable like the end that goes into the speedo. I've been through the whole hunt for cable deal as I moved my speedometer up to the handle bars and needed a longer cable than the stock one. I looked at a lot of cable ends and the Suz is an oddity from what I can tell.

When you insert the cable into the transmission rotate it (by the square speedo end) while pushing on it at the same time. When the tab on the cable gets aligned with the slot in the transmission it will just slide right into place. Tighten down the threaded cap nice and snug so there's no oil leak and you're in business.

Oh yeah, as long as you have the cable in your hands, make sure it's clean and lubricated. I've been told by several reputable mechs that the oil you use in the bike is fine to use for the cable as well. Pull the cable out, wipe it down and apply a little to it. slip it back in the housing and yahoo. It's what I've done and have had no problem.

Jack

You can see if th engines output to the speedo is turning by pulling the cable & marking the thing the cable goes into & putting ever so slowly across the garage. You can also poke a small flatblade in & see if it turns easily. I havent tried that, but I susoect it shoukldnt spin easily, if at all, I owuld honestly expect it to not even turn. If that part turns when the bike runs (in gear & rolling) doesnt spin by hand when its in gear & shut off, then I would have to suspect the speedo,

I'm in Kalamazoo Michigan, and Minnesota is on of my favorite states, but its about a good 12 hour drive, (or more),  to your area. I think I know what Justin is talking about. I will try it when I get home.
Cant thank you guys enough.
Manoli