Feliz Navidad Senor Goo,
Either tire will work fine on your F650. Tire sizes can be a tad confusing. At least for me until I understood the numbers meaning. Thus, 140/80-17 is shorthand for a tire that is 140mm wide, with a height 80 per cent of 140 (132mm) and made for a 17 inch rim.
Clear as mud? Well, fortunately tires are flexible and a slightly wider and taller 150/80 will fit your rim. It might rub slightly on the monoshock or swingarm until it wears in. Especially if you order the blockier TKCs as opposed to the less aggressive tread Tourance. The 130/80 is slightly narrower and lower profile than what your bike calls for.
If you are ordering sight unseen I would get the 130/80 in TKC so you don't have to sand down the outer block tread slightly with a belt sander. BTDT.
The thing is, different tire manufacturers sizing can vary even with the same numbers. I remember a time in Baja when I was riding a rear tire with the cords showing and I was desperate for a tire. I needed a 120/90-18 rear desperately and found a guy out in the middle of the desert who had some 130/80-18 full knobs stashed for the Baja 1000. He sold me one for a hundred bucks and I was ectstatic. The thing is it was an aggressive Dunlop knobby and I was riding a BMW street bike. But I had to make it 1500 miles back to work by monday and it was Saturday afternoon. So I didn't mind the smell of burning rubber as the outer blocks wore down on my shock, or the zzzzzz, zzzzzzz, of the tire bottoming on the rear fender over every large bump in the road for the first few hundred miles.
Others who actually own an F650 and have come across your situation will hopefully chime in with better answers, but I would go for the 130/80 unless someone says different.