BSA M20,M21 FACTORY WORKSHOP MANUAL THAT COVERS BOTH 500cc & 600cc, SIDE-VALVE RIGID AND PLUNGER MODELS FROM 1948 TO 1963 MODELS, BUT THE 1946 & 1947 MODELS ARE VIRTUALY THE SAME AS WELL, THE OLD NAME FOR THIS WORKSHOP MANUAL IS SERVICE SHEETS.  IT COVERS HOW TO DO VITUALY  EVERY MECHANICAL REPAIR/RECONDITIONING  JOB ON THE ENGINE,GEARBOX, CLUTCH AND CARBURETTOR  TOGETHER WITH HOW TO REPAIR AND RE-CONDITION THE ROLLING CHASSIS AND CYCLE PARTS INCLUDING HOW TO SERVICE AND REPAIR THE BRAKES TELESCOPIC FORKS AND REAR SUSPENSION UNITS AND IT ALSO HAS A LOT OF INFORMATION ON TAPPET ADJUSTMENT,IGNITION TIMING SETTING UP THE CARBURRETTOR FOR NORMAL AND ALTITUDE RUNNING AS WELL AS TUNING THE CARBURETTOR AND FAULT FINDING (IT EVEN SHOWS YOU DETAILS OF HOW TO RE-CONDITION THE CRANKSHAFT ASSEMBLY. AND ALSO THE ELECTRICS INCLUDING WIRING DIAGRAMS CHECKING THE VOLTAGE OF THE ELECTRICAL CIRCUITS  ( THE MANUAL IS 63 PAGES THICK 126 PAGE SIDES WHICH IS THE SAME NUMBER OF PAGES AS THE ORIGINAL MANUAL AND SHOWS ALL ASPECTS OF  REPAIRING/RECONDITIONING THESE BIKES TO KEEP THEM MECHANICALY SOUND AND ROAD WORTHY. OVER 50 SOLD IN THE PAST 2 YEARS.ANY QUESTIONS PLEASE EMAIL