In 6th edition models with different movement speed may move at their full speed, as long as they remain in coherency.
So I'd say, that because Bikes can't run their running speed is always counted as 0", but the Beasts may run, as far as they want, as long as they end up being in coherency.
But because running counts for whole units, for the purpose of shooting, the Bike can't shoot, even if it didn't move.