By Cait Dooley

Imprints of bicycle gears line the sidewalk leading into a Jamaica Plain office that looks like a warehouse from the outside. There are bicycles locked to racks and bike frames strewn along side the brick wall.

Elijah Evans, 18, of Dorchester, the new Earn-A-Bike coordinator of Bikes Not Bombs (BNB), spends most of his free time, in the office.

It’s a customized building center: Inside, the walls are painted bright aquamarine and lime green; there’s a youth lounge on the second floor; and most of the space is dedicated to bikes in varying levels of completion, bike parts and tools that are neatly organized.

With his new position, Evans aims at fostering a safe haven for Boston-area youths. BNB, founded in 1984, is an organization with a focus on social justice, community building, education and, unsurprisingly, bicycles. BNB is also far reaching. The group sends 3,500 bicycles to places like Ghana, Guatemala and South Africa. BNB has its own fully functional bike shop, run by instructors and other members. It also runs a special program for youths 12 years and older called Earn-a-Bike.

Evans’ schedule can be chaotic. When he comes in the afternoon, he plans what that day’s course will cover, where they will ride, what instructor will be teaching the main lesson and a few other “housekeeping” tasks. Earn-A-Bike classes start at 4 p.m. and afterward there’s cleaning up to do. Evans also works at the BNB bike shop when he can.

The Earn-A-Bike concept is simple. Children pick their bicycle, take it apart and rebuild it. From the more than 5,000 bicyles donated each year BNB makes a commitment to spend an agreed number of hours rebuilding the bike and doing community service. Of the more than 250 youths who have participated, 95 percent of them are African-American, Latino or Afro-Caribbean from low-income households.

On top of spending about 30 to 40 hours a week at BNB youth offices and at the bike shop, Evans is a freshman at University of Massachusetts Boston with a full-time class schedule. His major is undecided but he said he wants to concentrate on African-American studies and political science. Finding a balance can be tough, but he’s had experience.

“When I leave here from 7:30 p.m., when I get home, it’s hard to transition into getting my homework done