James has the power of the internal flame which makes him pull of any fire attacks, but it also gives him the ability to go full out Burst.

When he transforms into his Burst Form, his hair turns into a blazing fire and the end of his hair extends to his tail. His fire attacks are also stronger. Plus, when he goes full out Burst he creates a ball of explosion around him. And as long he has rage, he can maintain Burst.
He goes out of Burst Form when he has released all of his rage or when he's done with his enemies.

James (fox) © me