BSA B50
500cc Singles

BSA B50 BACKGROUND
BSA built its business and its reputation on big singles. The 350cc and 500cc Gold Star dominated the off-road market from the late 1930s to the early 1960s. By this time of course, the state of the art had moved forward considerably, and the heavy Gold Star couldn't compete with lighter 2-strokes from Europe and Japan. By the late 1950s, BSA and Triumph were converting over to unit construction, but the Gold Star's design wasn't conducive to it. So, a whole new line of unit-construction singles was planned for the 1964 model year starting with a 250. It was soon bored and stroked out to make the 441 Victor in 1965, then again to a 500 in 1971. Around 5,700 B50s were built from 1971 through 1973, just as BSA was collapsing. It was built in three basic forms. The B50 SS was a 'Street Scrambler' designed specifically for the US market. The B50 MX was the off-road/motocross/competition version and the last competition bike BSA built. The B50 T was the 'Victor Trail'-edition, considered an 'enduro' in the parlance of the day, but would be referred to today as a dual-sport bike.
BSA B50 500 SINGLE
All unit-construction BSA singles were spun off the original 250cc Star in 1959. Bored all the way out to 84mm and stroked to 90mm, the resulting 499cc's made 34 horsepower, compared to the paltry 15 horses that it started out with as a 250. All that power, 28 pound-feet of torque, and the tremendous loads created by that big crank, rod and piston assembly spinning and reciprocating at 6000 rpm. Mechanical loads, vibration and crankcase pressure conspired to make these notorious oil leakers. These bikes also needed a 5-speed, really bad. They had tons of torque, but at nearly 300 pounds, were much heavier than their 2-stroke competition.

BSA B50 500 Singles YEAR-BY-YEAR

1971 B50 SS

The street version of BSA's big unit-construction 500 single. Conical hubs & forks from the A65.


1973 B50 MX

BSA's last year, and the last year for their big 500cc single. The MX was a lightweight motocrosser, although too heavy to compete with 2-strokes of the era.

Check out these BSA BOOKS

BSA - THE COMPLETE STORY


BSA MOTORCYCLES: THE FINAL EVOLUTION


HISTORY OF BSA MOTORCYCLES


BSA: ILLUSTRATED MOTORCYCLE LEGENDS, by Roy Bacon


HOW TO RESTORE YOUR BSA ROCKET 3 & TRIDENT


CHILTON’S BSA MOTORCYCLE REPAIR & TUNE-UP GUIDE


BSA SINGLES 1945-1963 GOLD PORTFOLIO


BSA SINGLES 1964-1974 GOLD PORTFOLIO


BOOK OF THE BSA - OWNERS SHOP MA NUAL, PRE-WAR


BSA 350, 441 & 500 SINGLES, UNIT CONSTRUCTION 1958-1973


BSA CLASSIC MOTORCYCLES


BSA & TRIUMPH TRIPLES: GOLD PORTFOLIO 1968-1976


BSA UNIT SINGLES: COMPLETE STORY


BSA A7 & A10 TWINS, 1957-1962, by Haynes


BSA A50 & A65 TWINS: ALL MODELS


ILLUSTRATED HISTORY OF BSA MOTORCYCLES


BSA TWINS A7 & A10 1946-1962, GOLD PORTFOLIO


THE BSA GOLD STAR


MAINTENANCE MANUAL FOR BSA M20


SECOND BOOK OF THE BSA 500 & 650 TWIN 1962-1969


BSA PRE-UNIT SINGLES WORKSHOP MANUAL, by Haynes


TRIUMPH TRIDENT & BSA ROCKET 3 WORKSHOP MANUAL, by Haynes


BSA BANTAM WORKSHOP MANUAL 1948-1971, by Haynes


BSA UNIT TWINS, THE COMPLETE STORY


BOOK OF BSA SINGLES & V-TWINS 1936-1952


RUPERT RATIO UNIT SINGLE ENGINE MANUAL, BSA & TRIUMPH


RUPER RATIO, EVERYTHING BUT THE ENGINE, BSA & TRIUMPH


BSA A50 & A65 TWINS 1962-1973, Haynes Workshop Manual


BSA GOLD STAR & OTHER SINGLES, by Roy Bacon


BSA MOTORCYCLES SINCE 1950,BR>

BSA UNIT SINGLES OWNERS WORKSHOP MANUAL #127, 1958-1972, by Haynes


BSA TWINS 150 & 165 GOLD PORTFOLIO, by RM Clarke


ILLUSTRATED BSA BUYER’S GUIDE, by Roy Bacon


BSA BANTAM, by Owen Wright


BSA PRE-UNIT TWINS, by Mick Walker


BOOK OF THE BSA OHV & SV SINGLES - 250cc 1954-1970


BSA TWINS & TRIPLES, by Roy Bacon


TRIUMPH & BSA TRIPLES: THE COMPLETE STORY


BOOK OF BSA TWINS, ALL 500 & 650 1948-1962, by Floyd Clymer


BOOK OF THE BSA OHV & SV SINGLES 1945-1954: 250, 350, 500 & 600


BSA BANTAM BIBLE, ALL MODELS 1948-1971


WHERE BSAs DARE: BSA’s 1952 ISDT GOLDS & MAUDES TROPHY


ILLUSTRATED MOTORCYCLE LEGENDS: BSA, by Roy Bacon


BSA BANTAM ESSENTIAL BUYER’S GUIDE


BOOK OF THE BSA BANTAM


BSA 500 & 650 UNIT TWINS, Clymer Repair Manual


BSA COMPETITION HISTORY


BSA MOTOR CYCLING ANNUAL, 1937, Kindle






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Last updated 3/11/17

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