A self-portrait of the filmmaker as a promiscuous homosexual, the German import "Taxi zum Klo," now at the K-B Janus, runs down like an exhausted jalopy after a fairly disarming, promising start.

I don't think it's the homosexuality that accounts for the inertia, although that angle certainly will limit the movie's public. Writer-director Frank Ripploh, a former secondary school teacher who dabbled in amateur acting and filmmaking before raising the money to shoot this frankly indiscreet memoir, depicts his sex life with pornographic candor, including one interlude of rough interplay whose kinkiness might be politely described as repulsive.

What sinks the movie as time slogs by are acting deficiencies and the pervasive dinginess of the German social setting the characters seem to inhabit.

The principal figures re-create their real-life roles under their real names. Ripploh, a contented cruiser, becomes involved with a vaguely endearing dullard, Bernd Broaderup, a theater manager who values sexual fidelity and cozy domesticity. One day, Ripploh gets so annoyed with Broaderup's passive disapproval and reluctance to swing that he comes out publicly by attending class in the harem costume he wore the night before to a masquerade ball.

This gesture apparently cost Ripploh his job and seems to be what inspired him to try professional filmmaking. He shot "Taxi zum Klo" in 16mm for about $50,000, and it began attracting critical attention when it won a prize at a competition in Saarbrucken.

The title, which means "Taxi to the Toilet," is drawn from a sickly funny episode where Ripploh, fleeing treatment for hepatitis at a hospital, flags a taxi and keeps hunting sexual gratification at public bathrooms. When he finally spots a potential partner, Ripploh is left cooling his heels after the stranger uncovers the hospital nightgown tucked absentmindedly inside his trousers.

At best, Ripploh reveals a knack for satirizing his own heedless carnality and general sloppiness that suggests comic affinities with Henry Miller or Cheech & Chong. A self-deprecating humor is his most agreeable and presentable trait, but it doesn't provide him with a comic identity that sustains the movie over feature length.

However, Ripploh isn't attractive or personable enough to get away with his outrages, which slop over the boundary of burlesque into sordid hardcore sex. There's also no dramatic urgency about the affair between Ripploh and Broaderup, and the more one sees of them, the more tiresome their company becomes.

There is, furthermore, a peculiarly depressing undertone about the places Ripploh frequents -- not only the toilet stalls but also his drab apartment and classroom. The most revealing aspect of "Taxi zum Klo" may be this unwitting intimation that Germany could use a lot of sprucing and toning up. The joint looks poorer than one imagined. Ripploh is supposed to be doing relatively well for himself because he's a teacher, at least by Broaderup's estimation, but if so, appearances are deceiving.

One amusing detail: Ripploh the teacher's subject is sex education. While the classroom scenes look utterly harmless -- trivialized anatomy lessons punctuated by the teacher's twerpy clowning around -- Ripploh seems an inspired choice to undermine confidence in a dubious subject.