Classic components

Launch model Villiers two-stroke engines had internal bob weights to their crankshaft and an outside steel flywheel. Later, the Wolverhampton maker replaced this with a flywheel magneto, with its rotor serving as the engine’s outside flywheel.

Villiers unveiled their 269cc single cylinder two-stroke engine in autumn 1913, its sparks supplied by a front-mounted, chain-driven magneto. This concept applied to the Mk.II, Mk.III and early Mk.IV 269cc units. Late in the Mk.IV series (1921) the bacon slicer outside flywheel was replaced by a Villiers-built flywheel magneto.

In hindsight, these, with 8¼inch diameter rotor, were known as the ‘large’ model.

Designed in 1920 by

Frank Pountney, the unit was progressively updated and altered for differing requirements, but its basic concept remained for all Villiers flywheel magnetos. Of two pole (correctly pole shoes, which separate the magnets) design, it was initially for ignition only with its ignition coil, condenser and points triggered by an engine mainshaft mounted cam fitted to the backplate (stator). The magnets were mounted to the enclosing rotor’s internal rim.

Soon, direct lighting coils were offered, and then rectified systems for battery charging, employing Westinghouse metal rectifiers, often made by Villiers under licence.

The first ‘small’ model Villiers flywheel magnetos (with seven inch diameter rotor) were fitted to the 1922 season 147cc Mk.VI-C engine, but within two years they started appearing on other models, beginning with the 172cc Sports engines in 1924, Brooklands (1925) with racing magneto and Super Sports (1926) 172cc engines with racing and sports flywheel magnetos respectively.

To improve both ignition and lighting, the number of rotor-mounted magnets was increased, improving output and the number of pole shoes fitted was increased accordingly… Well, almost!

Some six pole rotors only have five magnets, with the sixth a dummy and there were rare odd instances of six pole rotors fitted with only four magnets and two dummies for specific requirements. Four pole rotors appeared circa 1933/4 and six pole slightly later. To confuse further, some engines changed from two to four pole or two to six pole rotors during their production run, the Junior De Luxe (autocycle) engine had a three pole rotor and the 98cc Midget engine (1931-1940) started life with a two pole rotor, changing to four and then six pole rotors, and a few used three pole rotors.

The number of lighting coils fitted to the six pole magnetos varied to suit requirements – for example, separate coils serving headlight and tail-light, each with their own wiring circuit. And in some cases, stator fitments remained the same, but different outputs were generated to power either an 18 or 24 watt headlight bulb, achieved by using respectively a 1⅛ inch or 1⁄ inch wide rotor.

Flywheel (rotor) weights varied on request, such as heavier flywheel for trials applications.

Much early literature (up to the Second World War) states an ignition points gap of ⁄ inch; this equates to 15 thou (0.015 inch) which is found in most later literature to mid-1950s, when the range 12-15 thou was quoted. Although outside this feature, the points gap for Dynastart systems is 20-22 thou and – bizarrely – later NVT literature quotes up to 40 thou. Unsure where that came from!

While Villiers flywheel magnetos were supplied to suit specific engines to maker’s requirements, there’s lots of interchangeability, but minor modifications may be needed. For example, the three pole flywheel magneto commonly fitted to the Villiers Junior DeLuxe engine can be retro fitted to the earlier Junior engine as a replacement for the two pole device, but due to increased direct lighting output, the bulbs need uprating.