B.S.A. 4.96 h.p. O.H.V. Blue Star Model Q-21
ENGINE. 82 x 94 mm. ; enclosed O.H.V. gear; special cams; high compression piston; heavy valve springs; sports plug; pump Carburetter; upswept exhaust pipes.
LUBRICATION. B.S.A. sump type; 4 pints; pressure gauge in tank; pressure feed to big-end.
TRANSMISSION. ½ x .305 front chain totally enclosed and specially lubricated; 5/8 x 1/4" rear chain; engine cush drive; dry plate clutch; B.S.A. four-speed gearbox; foot gear change.
FRAME. Duplex cradle type with forged top member and integral sidecar lugs: flexibly mounted handlebar; saddle tank holding 3¼ gallons; Dunlop Fort 3.25-19 tyres; 7" x 1 3/8" brakes; hinged rear mudguard; valanced front mudguard (as illustrated) extra; steering damper ; quickly detachable rear wheel ; constant wheelbase front forks.
EQUIPMENT. B.S.A. controls with twist grips; ratchet front brake ; complete tool kit; pillion seat standard, or detachable carrier, if specified; Lucas 6 volt electric lighting set; tank instrument panel , electric horn; magdyno shield; Terry saddle; air cleaner.
FINISH. Black and chromium ; Chromium and green tank. Wheelbase 54" clearance 4 7/8"; saddle height 29¼".