Gs500f 2005 revs up but down extremely slow

[Quinn]

If anyone has an idea of what's going on I would really appreciate it!  https://www.youtube.com/watch?v=TLRVuZFstsE&feature=youtu.be

[The Buddha]

Hanging throttle cable is my first guess from your video clip. Followed by lean jetting as in - from the factory its got crappy jetting.

I don't think its a intake vacuum leak, the revs are far too even for that, and your motor isn't raspy enough either. But being 15 yrs old and made of Chinese chit materil, its probably worth it to just make sure its not an intake vacuum leak because its an easy check. So Check that too.

Cool.
Buddha.