Dean Keates scored what could be the solo goal of the season at Boothferry Park.
Hull were drifting aimlessly late in the first half when Keats sent a 35-yard volley screaming past Rhys Evans.
Keates, a non-contract player whose previous club was Walsall, gave a gutsy performance in midfield to lift Jan Molby's struggling Tigers.
Molby, under pressure from the fans over Hull's poor start to the campaign, watched an agonising first quarter in which his team produced groans from the crowd.
It was bad enough when a misunderstanding between Justin Whittle and Matt Glennon almost produced an embarrassing own goal. Whittle attempted to head back to the keeper, but Glennon was rushing out and flattened his team-mate in a collision.
Fortunately the ball bounced just wide, but it was even worse when Orient's Ciaran Toner was unmarked when he buried Carl Hutchings' low cross into the back of the net from 12 yards after 19 minutes.
Steve Watts should have made it two four minutes later, but headed straight at Glennon.
Hull produced nothing in the first half hour, but an Ian Ashbee drive that had Evans scrambling served notice that there was still life in Molby's side.
Keates proved the point four minutes later although Orient hit back with Toner almost scoring within 20 seconds of the restart.
The second half generally went Hull's way, but there were no more goals as the respective strikers showed that scoring is not easy.
Hull's Gary Alexander and Gary Bradshaw missed two each and Watts volleyed over and then headed straight at the keeper again in the space of a couple of minutes.
Hutchings starred for Orient, but midfield honours belonged to Simon Johnson who is on loan at Hull from Leeds United, with his energetic running deserving better reward