By Jeff Yorke Until recently Krytonite and Citadel, which both retail

for $32.50 pretty much had a lock on the bicycle lock market. Within the last several months, however, Master Lock Co. of Milwaukee has begun marketing their "Crime Fighter 50" bike lock, which retails for $23.50 and has a one-year guarantee of up to $300 against being "broken or opened by forceful means." Krytonite and Citadel each have basically the same guarantee, paying up to $350 and $250, respectively. The price of these locks seems high until compared to the typical $160-$300 cost of a new bike. Although there is no way to prevent 100 percent of the bike thefts, bike machanics and salesman around the Beltway agree that locking a bicycle with these case-harden steel inventions will deter at least the casual bikenapper. But as Michael McGovern of Cycles & Sports, Inc. in Northwest said, "You just have to pay more attention to where you park your bike." James Battle of the Metropolitan Police suggests cyclists park and lock their bikes in well-lighted, public and busy places. He said bicycle thefts in the District were down 33 percent this past June: 142 stolen compared to 212 in June 1981. In July the total bikes stolen jumped to 226 but was still down 13.7 percent from 262 the year before. Battle credits the decline to bicyclists' precautions. Many office buildings now offer bike racks to their employees. Metro offers some 300 protected lockers throughout the system which house the entire bicycle. A lock is built into the door and the lockers are in view of the kiosk. They can be rented for three months for $25, six months for $45 or for $70 a year. A $10 key deposit is required. For information call 637-1327.