Other source:
After 70 days of hard training with King Kai, Goku has gotten much stronger and faster. But, the Saiyans are going to arrive the next day, so Goku speaks to Master Roshi telepathically through King Kai. He asks him to use the Dragon Balls to wish him back. Suddenly, King Kai realizes that he forgot to account for the time it will take Goku to go back down Snake Way. With no time to waste, Goku leaves King Kai's planet and races down Snake Way.
