First Post throttle cable

yHi all , I'm hoping someone can help with a problem I'm having . I took the carbs off the bike as it had been sitting for years before I bought it . The disasembly and clean went fine ,but when I tried to mount the carbs the throttle will not snap closed when you let it go . If I just pull the cable by hand and let it go it will snap closed . when I hook up the cables to the twist grip it closes very slowly . I've obviously missed something in the assembly . Any help is appreciated  

Welcome.

One of the cables has to be binding somewhere.
Check that the cables are not getting pinched in the throttle grip housing.
One runs over top, one below, and they can't get squeezed by the halves of the casing as you tighten it up.
Also make sure to grease the ends of the cables and where they route through the throotle case/right hand switces.

Also the routing of your cables through the bike can effect it.
Too tight a bend in the cables, and they won't work freely.
Reroute the cables, avoiding sharp bends.

Perhaps some lube is in order.

Does the throttle tube turn freely without the cables attached?