A state judge sentenced an operator of a Waipahu motorcycle chop shop to 18 months in prison and to probation Wednesday, a punishment criticized as lenient by a city deputy prosecutor.

Circuit Judge Colette Garibaldi sentenced Toan Huynh Nguyen, 27, to five years of probation, the first 18 months of which he will serve in prison beginning today. Garibaldi also ordered Nguyen to repay his victims $235,436.

The prosecution said Toan Nguyen and his twin brother, Thang Nguyen, sold dozens of stolen motorcycles they had altered and repainted in their Twins Auto Body shop in Waipahu and got their girlfriends to falsely register some of the bikes.

Deputy Prosecutor Chris Van Marter said the sentence "grossly minimizes the defendant’s criminal conduct and the harm suffered by the dozens and dozens of victims as well as the insurance companies. In our view this sentence provides no deterrence to others who would operate chop shops."

The 60 victims include people whose motorcycles were stolen and people who unknowingly bought the stolen goods, which were later seized by authorities, Van Marter said.

He said the restitution amount does not include the $290,000 lost by insurance companies nor the losses associated with hundreds of stolen motorcycles police were not able to document. Van Marter said that from 2006 to 2009 the Nguyens and their co-defendants registered more than 300 motorcycles with the city.

The brothers were found guilty of first-degree theft, money laundering and tampering with government records. Sentencing for Thang Nguyen will take place later.

Garibaldi granted co-defendants Tiffany E. Nakata, 25, Thang Huynh Nguyen’s girlfriend, and Frances-Nicolette N. Freitas, Toan’s girlfriend, five-year deferrals on their no-contest pleas.

Van Marter said the Nguyens filed off the vehicle identification numbers of stolen motorcycles and replaced them with numbers of motorcycle frames they bought from salvagers on the mainland.