Four cylinder FNs 1914-1923

The first FN to offer full mechanically-operated valves appeared in 1914 alongside the original FN which retained its atmospheric inlet valves. I have described these earlier fours in a separate article. I don't pretend to be an absolute expert on dating FNs, but here is my considered opinion on the different M.O.V. 4-cylinder shaft-drive models which appeared just before and then after the Great War.

Side Valve (7HP) Models : 1914 - 1922

1914 Type 700 FN

Common features:

  • Gear change at right rear of tank
  • Foot operation of clutch, with ratchet [4,6]
  • Exhaust guard with 14 holes and FN
  • Tool boxes on carrier
  • Pillar mounted seat
  • Short valance only on rear guard
  • Hand brake lug on seat tube of frame
  • Exhaust exits at rear of engine

Features of pre-war models:

  • No sump extension, requires different clutch guard
  • Bicycle-type main fork
  • Footboard brackets loop under sump
  • Zenith carburettor, with manifold over top of motor

Features of post-war models:

  • Immediate postwar models probably very similar to 1914 model
  • Sump extension
  • Main fork extends to steering crown
  • Footboard brackets bolt into sump extension
  • AMAC carburettor with low level manifold [4]

IOE (8HP) Models : 1922-3

1922 8hp FN

  • Introduced into UK at Olympia Show, 1921
  • 1922 brochure [4] shows both 7HP (sv) and 8HP (ioe)
  • Early models have straight inlet manifold, with large nuts; later 2-bolt fixing (both types shown in [5] )
  • Early models have pillar mounted seats, later bolted directly to frame (both types shown in 1922 catalogue [4] ). Final model has longer nose on seat [1]
  • Early models have usual ZFN magneto, later [1,5] fixed ignition Scintilla magneto with HT leads at drive end
  • Exhaust exits from front of engine
  • Gear change at front right of tank
  • Fully valanced rear guard
  • Hand brake lug on right upper chain stay
  • Later models have longer lower front fork stanchions [1]
  • Dual operation of clutch (hand/foot)
  • Two matching levers on inside and outside of left handlebar: clutch and exhaust lift
  • Ratchet on Bowden hand brake lever and foot clutch pedal [4]
  • ‘Bulky’ AMAC double lever

1922 8hp FN outfit

 Useful Illustrations:

  • 1914 blueprints of engine [9]
  • 1914 works photo [8]
  • 1914 catalogue illustration [3]
  • 1914 restored bike [9,12]
  • 1923 final model [2]
  • All models [1]

 Sample Numbers:

  • 1914 (and 1919?) 70000 - 70176 [1]
  • 1920 -1921 71000 on [1]
  • 1922: 72000 on [1]
  • 1923: 74000 on [1]
  • Restored U1133 has Frame 70024 (note later style fork?)
  • Restored 8HP, leading link fork, has Frame 740077.T, Engine 2886 [10]

 References:

  1. Le Mythe des 4 cylindres en ligne 1904-1954, Reynaud
  2. Motorcycles to 1945, Vanderveen
  3. Golden Age of the Fours, Hodgden
  4. 1922 Sales Brochure
  5. Motorcycling, 16/5/23
  6. 1914 Brochure
  7. Verrall advertisement in CMC, 11/97
  8. A History of the World’s Motorcycles, Hough and Setright
  9. CMC, 4/85
  10. CMC, 8/83
  11. Line drawing, Motor Cycle, 31/5/23
  12. Classic Bike, 3/83
  13. Milledge article

Copyrightę Leon Mitchell 1998

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