Board Thread:Versus Debates/@comment-32832770-20170812151353/@comment-5085906-20170816181616

@IXaith

You're confusing chakra control with chakra reserves. And besides we do know that Rasengans and Bijuudama techniques get bigger the more chakra you apply to them. When against Sasuke, Naruto presumably wasted most of his chakra because after that the only techniques he was able to perform were shadow clones and briefly covering his hand with Kurama's cloak. If he had both halves of Kurama sealed in him, he naturally would have more chakra and he would have been able to release more of it and pool it into the Rasenbijuudama thingie (gotta look up the official name).

As for Naruto's chakra control, while an improvement from his genin days, it's still not as good as Itachi's or Sakura's chakra control. And because some techniques require precise chakra control, then that could be why Naruto can't master them - plus, as you said, he's also busy Hokaging and stuff.