All the bijuus have both yin and yang chakra within them, minato just separated them. Chakra regenerates over time, so it is useless to say that naruto has full chakra. I think kurama's chakra reserves were halved out during seperation, and got filled overtime with a single type of chakra (i.e. yin chakra within Minato and yang chakra within Naruto). Otherwise how the hell could naruto could counter the combined bijuudama formed by five bijuus using just one (whereas Hachibi didn't take the initiative beforehand knowing that he couldn't counter it effectively). I think everyone has noticed, that when naruto is in BM, then his Kurama form is just a chakra cloak, unlike the other jinchurikis who completely transforms into the tailed beasts themselves. Please don't say that naruto hasn't attained stable bijuu transformation until today. So, I think yin chakra provided shadow to the beast as expected. P.S - When Kyuubi takes the initiative to turn into a beast (not under Naruto's control), he uses the traces of yin chakra within him keeping him alive, to turn himself into a real beast (As seen in case of Nagato's fight "Chibaku tensei" and Naruto Movie 6), but this chakra is unavailable to Naruto for use, since its essential for the existence of Kurama itself.
