What should I use to clean the fuel lines and fuel injectors for my boulavard 800 c50 and my boulavard 650 s40?

And what you should use is SeaFoam.  How you should use it depends on the problems you are having.  No problems?  Juts clean it out by running a lot of fuel through it.  Preferably on curvy roads.

Fuel cleaners are more of a "feel good" fix than anything...
If you have sediment build-up,.. it won't remove it... and if it did, it would send it to places you don't want it to go...
If you have lacquered gas,.. any concentrate strong enough to dissolve it will likely not be good for seals... (and it might break free before fully dissolving, sending jelly gas further into passages)...

I'd just put some fresh, regular gas in it, and take a good long ride... regular gas already has detergents added... (don't use premium, it don't need it or like it, and it's usually been sitting in the station tanks a lot longer)...
If the bikes are running too badly for a spirited ride... you really should take the parts off and clean them manually...
Leave that gunky stuff in a cleaning tray, not in your engine...

Using additives to clean yer' carb, is like eating toilet paper to wipe yer' butt..
...

I used to do that on my GN 400, good to know it's workable on the S40 too

Although I can't say it made a huge difference, using Techron on several tankfuls seemed to help with both idle smoothness and backfiring after I got an S40 that had been sitting for several years. Seafoam had no effect. I'm sure taking the carb apart and cleaning it would have been more effective, but that was more than I was up to doing, at the time.