SPOKESONG, or THE COMMON WHEEL, by Stewart Parker; with music by Jimmy Kennedy. Musical direction and piano by Kevin J. McCarthy; costumes by Mary Ann Powell, scenery and direction by James D. Waring. With Raymond Hardle, Max Wright, Cynthia Crumish, Terrence Currier, Pauline Flanagan and Steven Sutherland. At Olney Theater through August 26.

The internal combustion engine comes in for some grand rhetorical abuse in Stewart Parker's "Spokesong," which opened Tuesday night at the Olney Theater.

"A car is just a hard shell of aggression for the soft urban mollusk to secrete himself in," says Parker's hero Frank Stock, who runs a sparsely patronized Belfast cycle shop threatened by bombs on the one hand and a proposed expressway on the other.

Stock sees the bicycle as the cure to most of civilization's problems, and most of Northern Ireland's. But no one else, including the schoolteacher he falls in love with while repairing her bike, is able to take him altogether seriously.

The automobile, he proclaims, is "a form of disguise. All its parts are hidden. No wonder they're using them as bombs.... A bicycle hides nothing and threatens nothing. It is what it does. Its form is its function.... Christ on a bicycle - you can see that. You can't see him driving a Jaguar."

Parker, as if anyone needed to be told, is an Irishman; and if his rhetoric and a Jaguar could have a head-on collision, the Jaguar would probably be totaled.

But "Spokesong's" rhetorical hijinks and lively songs are also, lamentably, an invitation to overacting. And several key members of the Olney company have accepted that invitation in rather emphatic fashion.

Starting with Max Wright (in an assortment of supporting roles) and Raymond Hardie (in the lead), this production has succombed to that Irish theatrical disease knows as "Marlarkey Sclerosis" or "Barry Fitzgerald's Revenge." Irish and non-Irish actors alike, under kts influence, start cranking their faces up like pieces of dried fruit and skipping around the stage as if engaged in a game of hop-scotch instead of a play.

"Spokesong" celebrates not only the bicycle but an increasingly rare form of political courage - the willingness to appear foolish. In lieu of highways, Frank Stock proposes to supply Belfast with 50,000 free bicycles, after the fashion of Amsterdam's "white bicycle" movement. Naturally, he is laughed right out of the public meeting where he makes his posposal.

When John Lithgow played the part at New York's Circle-in-the-Square last year, there was a sense of strength underlying his nutty love affair with the bicycle. But Hardie, the star of the original Dublin production, is merely - and inexorably and exhaustingly - cute.

Hardie's excesses are nothing, however, compared to Wright's. Potentially a funny actor, he roars through his various roles with a largely indistinguishable and incomprehensible set of comic mannerisms. Someone - director James D. Waring's name comes to mind here - should have told Wright to calm down his act.

Wright also appears, by the way, as a Trick Cyclist whose trick is that instead of riding a unicycle, he plays it like a guitar.

There are other cast members - notably Terrence Currier and Pauline Flanagan as Frank's grandparents - who have not succumbed to the general madcap anarchy. The flashback scenes of their 1890s love affair, conducted in the same unaltered shop, are affecting as well as funny. But otherwise the depth of feeling under the antics and accents in this production could be measured with a jeweler's gauge.

Still, the author is an astonishing fount of wit and wordplay. After a pet shop is fire-bombed, someone observes that "For one magic moment, it was raining real cats and dogs." A song called "Energy" includes a toast to "a full four-score-and-20 of/That which Casanova had got plenty of/And what Dante warned the cognoscenti of: /Energy."

And where else can one pick up a capsule history of John Boyd Dunlop's invention of the pneumatic tire, conceived (if Parker is to be trusted) as Dunlop's three-year-old son was complaining about the bouncy ride of his solid-wheeled tricycle, and the father's gaze fell on a suggestive piece of garden hose. CAPTION: Picture, Raymond Hardie and Max Wright in "Spokesong"