As you can see here, Goku states that the Kaio-Ken amplifies the users power, but only for the span of a single heartbeat. Yet in that time, Goku and Vegeta were able to have an entire fight sequence, with Vegeta taking the advantage. Later Goku uses the Kaio-Ken x3 and he...
Kaio-ken - Xeno Goku learns this technique after dying against his world's Raditz while training under King Kai. While using it and any of its multipliers, Xeno Goku's various capacities and techniques are all proportionally increased. However, the strain of using too high a multiplier and/or...