Washington's third annual Bike Week will start Wednesday with a free bicycle maintenance clinic, features races, commuter caravans and weekend pleasure trips and ends May 1 with a short spin on Capitol Hill with congressmen who support bicycle legislation.

Sponsored by local bike groups, the week of two-wheeled activities is designed to entice more persons onto bicycles, particularly commuters. Some of the thousands of regular bike commuters will lead commuter caravans downtown from areas around the District and dozens of Maryland and Virginia suburbs April 27 and 30 and May 1. For further information call HEY BIKE, 265-4317 or 966-6563.

Many of the events will be held on the Mall in conjunction with ACT'79, an ecology-health fair, April 27 through 30.

Bike Week includes a race April 29 with $1,000 in prizes at Walter Johnson High School in Bethesda (registration at 11 a.m.); bicycle commuter and camping workshops and displays on the Mall from 2 to 4 p.m. April 29 and 30; bike trips from the Mall to National Zoo at 10 a.m. April 28 and to Mount Vernon at 10 a.m. April 29.

A bicycle maintenance clinic will be held at 7 p.m. Wednesday at Arlington's Madison Community Center, 3829 N. Staford St. off Glebe Road near Chain Bridge. A bike mini-fair is planned for Montomgery Mall from 6 to 9:30 p.m. April 30.

A party will be held at Fletcher's Boathouse, Canal and Reservoir roads, where the public is invited to bring their bikes and beverages and meet members of Potomac Pedalers Touring Club, Washington Area Bicyclist Association, Federal Bicycle Council, National Capital Velo Club, 4-H youth programs and Downtown Delivery Service, and American Youth Hostels, most of which are sponsoring bike week.

On May 1, which will become National Bike Day if bills now in Congress become law, the public is invited to take a short bike ride with congressmen, including Sen. Carl Levin (D-Mich.) and Rep. Tennyson Guyer (R-Ohio), and to join in a 2:30 p.m. bike day celebration by the southeast corner of the Rayburn House Office Building.