“The Sunshine Boys,” now playing through Aug. 9 at Acadia Repertory Theatre, is surely one of Neil Simon’s funniest plays. A rambling two-hour series of one-liners and who’s-on-first routines honed during Simon’s early days as a gag writer, the script can make us laugh big laughs at every old-fashioned, human-foible joke.

The premise itself is the very stuff of Simon’s nimble-witted business, which has made him one of the most popular and successful playwrights in America. He presents us with Lewis and Clark, a vaudevillian comedy team that, after a hate-filled 11-year separation, is reunited to revive their signature routine for a TV special on the history of comedy.

Willie Clark plays the team member who lives with the illusion that retirement has not yet occured and that his nephew-agent, Ben, will soon be bringing news of work in a musical or a commercial. Clark waits in an old hotel on upper Broadway, where his pajamas yellow as he watches soap operas, eats cans of soup, and smokes forbidden cigars.

In the role, Eugene J. Tierney solidly captures that saturnine malevolence of an old man embittered by jealousy, loneliness, and out-moded talents. He projects a strong voice and character, and contorts his meaty jowls and saucerlike eyes to create the picture of a man who has made a career from dynamic expressions. He has a vague resemblance to W.C. Fields, and the likeness, which can be distracting in Tierney’s work — especially vocally — serves him well here. Occasionally, Tierney takes a little too long delivering the fast-paced repartee, but he’s the best thing this production, directed by Ken Stack, has going for it.

Crony Al Lewis, who perpetrated the breakup and has since retired to his daughter’s home in the countryside of New Jersey, is played sloppily by Bangor actor Steve Robbins. In trying to portray the philosophical side of this character, Robbins, who has often shown a natural talent for slapstick, slows the pace down to a dead stop in too many places, and we end up having to take it on faith that Lewis was once a king of comedy. Robbins stumbles over too many lines and is obviously uncomfortable with the dramatic demands of adopting a Jewish idiom.

Coincidentally, it is the actual enactment of the signature routine “The Doctor’s Office,” that is the least laughable element in this show because there’s no funny team if only half the team is funny. But, even if we’re only chuckling when we could be belly-laughing, the script is continually entertaining.

Lou Solomon nicely fits the role of the long-suffering nephew, and bit parts, played by Alan Gallant and M. Patricia Prendergast, are light and well-done. Though hideously padded so as to look like a candy-loving nurse, Katharine Tyson is quite delightful and refreshing in her brief, final-act appearance.

“The Sunshine Boys” will be performed 8:15 Tuesday-Sunday through Aug. 9 and 2 p.m. Aug. 9 at the Acadia Repertory Theatre. For more information, call 244-7260.