Citi Bike is facing a backlog of hundreds of worn-out bikes to rehab and replace for the summer because the former management left the bike share in such bad shape, union officials said.

When it was run by Alta Bicycle Share, workers were focused more on quick fixes than extensive repairs to make quotas and get bikes more quickly out on the street.

“We were understaffed,” said Citi Bike mechanic Evan Ryan. “We had to make and achieve quotas to bang all the bikes out.”

He added that the targets kept changing under Alta, and workers were never able to get in a groove where the bikes were in good shape.

Union officials say that 900 bikes still in the shop has really been slowing the ride-share in New York down. A Citi Bike spokesman said there are 600 left.

“There’s a backlog of bikes needed for repair,” he said. “We are working to raise the quality of repairs so they stay out on the street for awhile, and not come back in one to two weeks.”

The new bosses under Motivate, which now runs the bike-share program, have been focused on hiring more workers to do maintenance — bringing in mechanics from their other bike shares to speed up work for the summer — and doing more structural repairs that last longer.

About a dozen mechanics from bike shares in Chicago and Washington, DC, are tuning up and overhauling the 900 bikes in the Sunset Park section of Brooklyn to get them back on the road.

The bike-share programs in those cities are not as busy as New York City, where bikes have the highest ridership and get six to eight rides a day.

“They don’t have the type of ridership New York does,” said Nick Bedell, the lead TWU Local 100 organizer for the unionized bike share. “They get beat up more.”

Motivate considered contractors from local shops but decided ultimately to use bike-share mechanics from their other cities who know the design of Citi Bike and can overhaul as many 10 to 12 bikes a day.

Local shop workers can typically only do about eight a week, because the ride-sharing bikes are made differently, to prevent tampering and handle many rides a day, officials added.

“We are trying to get the bikes on the street as quickly as possible. It’s all hands on deck,” said mechanic Chris Chzambel, 29, of Chicago. “It saves time on the repairs.”

A spokeswoman for Motivate said they have overhauled almost all of their 6,000 bikes.

“Citi Bike has made enormous progress over the past six months to improve and prepare for peak riding season,” said Dani Simons. “We’ve added 30 mechanics and field bike technicians since April to ensure we can keep up with demand as peak ridership season starts.”