When a high-concept action-comedy becomes a hit despite slapdash scripting and single joke themes weaved into an emaciated plot, the ball starts rolling toward the inevitable: An even lamer sequel.

Thus was born the half-baked, ham-fisted "Rush Hour 2," another odd-couple buddy cop picture pairing Hong Kong detective Jackie Chan, king of the kung-fu action-comedy, with LAPD putz Chris Tucker, high-pitched hyperactive buffoon.

In the 1998 original set in Los Angeles, Chan and Tucker went against orders to rescue the daughter of the Chinese consul. This time they start their own investigation (against orders) when a bomb goes off at the U.S. embassy while Tucker is on vacation in Hong Kong. What this bombing has to do with the plot about a Triad counterfeiting ring isn't readily apparent, but the two are connected by Zhang Ziyi (the beautiful teenage heroine of "Crouching Tiger, Hidden Dragon"). She delivers the package bomb in the movie's opening scene and is wasted in the rest of the flick leading a gang of henchmen into ho-hum high-kicking combat with our heroes.

At once insipid and confusing, the story follows the now-crooked ex-partner (John Lone) of Jackie Chan's dead policeman father (got that?) as he smuggles millions of sophisticated phony $100 bills from Hong Kong to Las Vegas, where the bogus bucks are to be laundered through a casino.

Chan and Tucker follow along, sometimes of their own accord and sometimes as captives who have to escape in badly-staged fight scenes that have been slowed down to accommodate the rabid schtick and meager sparring abilities of the American half of this comedy team.

Director Brett Ratner frequently kowtows to Tucker's urge to upstage, especially in the Hong Kong half of the film as he sings like Michael Jackson at a karaoke bar, tongue-ties his pidgin Cantonese and chases baddies through Chinese street markets squealing, "Out of the way! LAPD!" Tucker also clowns through a lot of mock kung-fu movements and recycles really tired Chinaman jokes ("All y'all look alike!") throughout the movie.

Some of this might have played well enough if "Rush Hour 2" wasn't so lifeless, but the banter between Chan and Tucker hasn't an ounce of spirit and even the action scenes feel stale and lethargic. The first of a very few laugh-out-loud moments doesn't come until the second act: Chan and Tucker wrestle for the binoculars while watching a sexy, possibly crooked US Secret Service agent (Roselyn Sanchez) undress during a stake-out. "Victoria's Secret," Tucker squawks, licking his chops. "Spring catalog, page 27!"

As with the first "Rush Hour," several scenarios are lifted wholesale from "Beverly Hills Cop" and the ratio of the likable Jackie Chan to the grating Chris Tucker is unquestionably tilted in the wrong direction. Some of Chan's charm comes through anyway, and he does get one great fight scene at the crowded tables of a Las Vegas casino. But the only unhindered entertainment value in "Rush Hour 2" comes from the outtakes that accompany the closing credits. If the scripted stuff were one-fifth as funny as these goofs, the movie might have been worthwhile.