Six motorcycle thieves who were part of a city-wide ring that stole dozens of high-end bikes by hot-wiring them or just throwing them in the back of a van were busted Tuesday after a months-long NYPD investigation, police sources said.

“Most of them were in the street and they were hot-wiring them,” a police source said. “There were times they would throw them in a van.”

“It’s crazy,” the source said.

Operation “Midnight Grinderz” began in October after Detective Scott Munro went out to investigate a rash of motorcycle thefts in Queens.

He noticed a minivan casing several parked motorcycles on Parsons Boulevard, pulled it over and determined that the driver, Craig Williams, 39, had been arrested for auto theft in the past, the sources said.

Video surveillance from the area captured the same 2008 Chrysler Town & Country minivan involved in the theft of a cycle, the source said.

Cops then used GPS to connect the driver to several other thefts. Detectives determined that multiple suspects were ordering specific bikes, stealing them and then brokering their sale.

In all, 29 motorcycles were stolen by the group, the sources said.

Five men were expected to be arraigned in Queens on Tuesday. A sixth man was in custody in Pennsylvania.

Williams was charged with grand larceny, criminal possession of stolen property and conspiracy in several of the thefts.

Cops are still seeking a seventh suspect they believe was involved in the ring.