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

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

• 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

 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

Copyright© Leon Mitchell 1998

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