United were away at Fleetwood for their latest Saturday morning youth fixture.
And the top of the table clash brought a dominant and fluent performance from the visitors as goals from Nic Bollado and Robbie Swinburn gave the Blues a cushion, and eventually the victory.
The Cod Army had a man sent off just after the break, and they bagged a late consolation, but it was Carlisle who came away with the spoils.
"The attitude from the lads was superb," youth boss Mark Birch said. "They dominated from the off and worked really hard for each other.
"We could have scored more, but that's being greedy. Overall we're very pleased with what we saw."