Five years ago the Beasties were seen as a novelty. Now the rap world is taking them seriously.

''The fact is that 'funky' is the most misused word in music today'', exclaims Michael ''Mike D'' Diamond, the Beastie Boys who tends to get the most impassionated. The other Beasties look up from their Indian food and shout their agreement over the racket-being made by a party of seventeen French tourists that has surrounded us in a midtown Manhattan restaurant. ''A lot of people are getting over playing 'chink-chink-chink- on the guitar and people saying they're funky'', says Adam ''Ad-Rock'' Horovitz. ''That shit isn't funky!'' Diamond called out. ''You just got to put on a James Brown record if you want to know what the word means,'' says a dead-serious Adam ''MCA'' Yauch, shaking his head. ''James was defining that word on a regular basis.''

They may not be the Hardest Working Mean in Show Business, but the Beastie Boys have learned a thing or two about funk since their quadruple-platinum debut, ''Licensed to Ill'', exploded in a hail of Budweiser, bong hits and caged dancing girls in 1986. The years since have been largely spent buying records and soaking up sounds, and their new album, ''Check Your Head'', is a glorious train wreck of styles -- old school rap, echo-drenched psychedekia, blaxploitation-movie themes, even bluesy organ-trio jazz. It somehow emerges as the first genuine punk-funk fusion, if that label hasn't been ruined by previous applications to dozens of unconvincing Next Big Things.

Five years ago the Beastie Boys were the ones whose funkiness was on the line. They were three white, Jewish New Yorkers, formerly a teen hardcore band called the Young and the Useless, serving up a snotty cartoon version of hip-hop culture -- a grungy chronicle of nonstop partying and unsafe sex, fueled by throbbing Led Zeppelin guitar riffs -- that quickly became the best-selling rap album ever. Concerned observers saw them as a novelty at best, maybe even the end of rap as we knew it.

Back them no one would have believed that, the Beastie Boys would still be an issue now. Yet after the legal battle with the Def Jam label (the Beasties said they were owned royalties; the company said they were taking too long to deliver their second album) and a move to Los Angeles, they released ''Paul's Boutique'' on Capitol Records in 1989. A brilliant, dizzying masterpiece of surgical-strike samples and pop-culture detritus, it barely went gold but gave the group new critical respectability. Now, three years later, ''Check Your Head'' is as different from ''Paul's Boutique'' as that album was from ''Licensed to Ill'' and as groundbreaking as either one. They won the fight for their right to party, and then, while no one was looking, the Beastie Boys turned into one of today's most consistently creative bands.

And yes -- ''band'' is indeed the appropriate description. The Boys play instruments on about three quarters of ''Check Your Head'' (the same lineup as in their punk days -- Horovitz on guitar, Yuach on bass and Diamond playing drums -- augmented by itinerant carpenter Keyboard Money Mark Nishita), with samples woven and injected into the mix. They're not exactly technical aces, but playing hasn't sounded this much fun since the first Ramones record.

''A lot of the theory this time was 'Okay, let's make a record that's like all dope break parts of records we listen to,''' Diamond says.''We wanted to play because we were inspired by the music we were listening to all the time.''

If there's a secret to the Beastie Boys' survival, it is this willingness to wear their influences on their raggedy sleeves. They have never claimed to be anything they're not and or to play anything but music they like listening to. From the street-corner couple trading of ''Pass the Mic'' (first single) to the thrash metal of ''Time for Livin' '' or ''POW'' and ''In 3's,'' on ''Check Your Head'', the Beasties are going back to the roots of rap and roots of their own.

To make room for the music, the rhymes on ''Check Your Head'' are fairly rudimentary, but the theme that comes through the clearest is the group giving thanks. ''It's no question life's been good to me,'' Diamond raps on ''Professor Booty,'' while on ''Pass the Mic'' he claims, ''To tell the truth I am exactly what I want to be.'' One track is simply titled ''Gratitude.'' After so many accusations that they've exploited black music and culture to get to the top, the Beastie Boys have apparently decided to make their respect explicit this time around. That's why bass-slapping guitar-scratching longhairs faking the funk are no joke to the Beastie Boys these days.

''The bottom line with a lot if bands that 'funk' is being applied to is that they don't really listen to funky and aren't versed in funky,'' according to Diamond. ''Like, you know, Gordon Lightfoot.''

Where else but L.A. could the Beasties build their dream studio, complete with basketball half-court and skateboard ramps? It's no wonder they spent three years jamming before deciding it was time for some new product. ''People think it's taken so long to do this album, but it kinda seems like when we were doing it, it only took a few months,'' says Horovitz.

''We could have released this stuff as six different phases on six different albums,'' claims Diamond. ''Isn't that the trend now? Instead, it's just six different phases on one album.''

Los Angeles has definitely left its mark on all three Beasties. The most obvious victim is Horovitz, 25, who has kept an acting career going on the side (he currently costars in the biker fantasy Roadside Prophet) and has been linked to several high-profile starlets, including Ione Skye, with whom he's had a lengthy, on-going relationship. Diamond, who's twenty-six, is the Beasties' liason to the press, their record company and the rest of reality. He owns part of a new clothing store that sells classic sneakers (the Boys, by the way, seem devoted to vintage Adidas, circa 1974) and customized t-shirts.

The biggest surprise has been the twenty-seven-year-old Yauch. The scruffy leather-jacketed Beastie Boys on the ''Licensed to Ill'' sleeve has switched to a macrobiotic vegetarian diet and spent last year traveling in Asia on some sort of spiritual quest. Musically, he's the group's secret weapon; his bass is a solid anchor for the tracks, and even his rhyming style has improved the most noticeably.

Taken together, these are hardly the beer swirling, groupie-devouring fiends who terrorized the world in 1987. In conversation, they still drop perfectly placed non sequiturs and riff at length on parenthetical thoughts, but it's hardly the chaos that got them banned from the CBS Records offices and reduced some early interviewers to tears.

Maybe it's the laid-back L.A. influence, maybe they're just tired, or maybe the Beastie Boys -- the last of the Great White Dopes -- have actually grown up. Despite the disappointing sales of ''Paul's Boutique'', they have only good things to say about Capitol Records. ''Leaving Def Jam was kind of a blessing in disguise,'' says Diamond, ''because we can make whatever record we want.'' Not that they have any ill feelings for Def Jam or its chairman, rap mogul Russell Simmons. ''I heard he was getting mad at us because we didn't want to throw beer at each other anymore,'' says Horovitz, ''and that was our job.'' But according to Diamond, ''Russel did say that if we came out with 'Paul's Boutique' again and wore our baseball caps sideways, we'd sell 8 million records. Says people are ready for that shit now.''

It remains to be seen, however, whether people are ready for rappers playing their own instruments for the first time. Are the Beasties concerned that especially after the confusion that greeted ''Paul's Boutique'', this album may be too disparate for their audience? ''People who are making hip-hop records definitely understand where we're coming from because they're used to hearing funky instrumental shit,'' says Diamond. ''People who only listen to hip-hop in hip-hop form, it might be a little hard for them to hear at first.'' The real following for ''Check Your Head'' may prove to be the Red Hot Chilli Peppers/Lollapalooza generation kids, and the Beasties are promising a lengthy tour, their first since the ''Licensed to Ill'' days, to get it to them (rumors have them sharing a bill with Cypress Hill and Sonic Youth.)

They did a few shows last year, including a packed, sweaty date at a New York club where teenage fans were stage diving in droves and literally hanging from the rafters. At the time, the new songs weren't finished, and most of ''Paul's Boutique'' is too complicated to re-create onstage, so the bulk of the material came from ''Licensed to Ill''. ''It was nice recapping old times to do those songs,'' says Yauch, ''but by the time we did the next show, I was like 'Damn, this shit is old!' It was like bringing out the antique-coin collection.''

The Beastie Boys claim to be content in Los Angeles, but it's clear they relish being back in their native New York, even when it means spending all their time dealing with the press. They're happy not to have to drive everywhere they go and be able to go to Knicks basketball games (scared off by the power chicness of Lakers games, they say they've never even bothered to go). ''I feel no compunction to defend L.A.,'' says Diamond. ''People criticize it, and for the most part, it's well founded.''