JAP 5 Wico Impulse Magneto

Type A or Type CJ Magneto

Earlier Jap 5 engines were fitted with a Wipac Type A Magneto which was bolted down onto a mounting plate on the side of the engine. Later Engines were fitted with a Wipac Type CJ, which has a 2 bolt flange directly onto the engine’s gear casing.

In the photos below, you can see both engine types. The newer flanged arrangement was used on engines from about 1950 onwards. The slotted bolt holes on the magneto housing on the type CJ allowed for easier adjustment and control of ignition timing.

The original JAP 5 engine is fitted with a base plate mounted Wipac Impulse Type A magneto, specification A-576 BZ. It is driven , at engine speed from the same gear wheel (driven by the camshaft gear ) as the governor. The magneto therefore creates a spark plug spark on every rotation, so it creates an idle spark at the top of the exhaust stroke. (as well as the required spark at the top of the compression stroke )

The Series A Wico magneto is modern in every detail (1940’s ! ), and is rugged but light in weight, die-casting being used wherever practical. It combines the well known Wico principle of die-cast magnet rotor with laminations and magnets cast integrally, and die-cast pole shoes. The adjustment of breaker points is by an eccentric headed screw. Self filering circulating lubrication is employed.

This is the magneto fitted to my machine , as found. It is the newer type CJ magneto. Everything appears to work OK, except that neither of the “STOP” buttons work. I will open it up to investigate further.

With the Magneto removed, the magneto drive coupling is visible. This is driven by the same gear as the governor spindle on the opposite end.

This is the magneto fitted to my machine , as found. Everything appears to work OK, except that neither of the “STOP” buttons work. I will open it up to investigate further.

Will also have to figure out what modern oil should be used, per attached nameplate.

When that little brass , circular , knurled , spring loaded cover is pulled outwards, a small hole is visible. The oil is inserted thru this little filler hole.

See here with the top bakelite cover removed. This is a black Bakelite moulding affording easy access to the coil and forming a one-piece, moisture- proof terminal-insulating block through which the High Tension current is led. ( Notice the brass spring tab protruding from the dark red coil which comes into contact with the similar spring tab on the inside top of the black bakelite cover ) The cover is held on the housing by four fillister-headed screws which have snap rings on them to prevent separation of the screws from the housing when the cover is removed.

The coil assembly consists of a large laminated core section, and properly balanced primary and secondary windings, vacuum heated, impregnated under pressure and taped. It is mounted on top of the cast-in laminated cores of the main housing of the magneto with hold-down clamps securely anchored with fillester headed screws.

One end of the primary is connected to one end of the condenser, and at the same time to the movable breaker arm. The other end of the primary is earthed to the core, as is the inner end of the secondary. The live side of the secondary is provided with a meal contact on the outside of the coil which makes contact with a bronze spring on the inside of the black bakelite cover. This bronze spring contact terminates in the High Tension terminal, which consists of a brass insert moulded in the tower of the bakelite cover. The copper core High Tension lead fits into this and delivers the High Voltage pulse to the Spark Plug.

The coil is removed by first releasing the right hand side earth stud and then removing the two screws holding down the core clamps. Turn the magneto shaft until the magnetism no longer grips the coil core to the main housing, then pull up on the coil and it is free.

With the coil removed, the magneto rotor can be seen. It consists of two high-cobalt steel magnets and the rotor laminations. Also visible, is the black cable interlead to the stop button on either side , which is connected to the live side of the condenser. By pressing either external “Stop” button this is grounded, thus stopping the engine.

With the end cover removed , by releasing the 2 spring clips, the condenser , cam and points mechanism is visible.

The points assembly , including the condenser was stripped out and the point contacts were cleaned.

By bending back the copper”STOP” tab, the terminal and insulating washers assembly is visible. The nut and bolt are dirty and appear corroded. On one side the terminal bolt is a brass type material and opened easily, while on the other side a steel bolt was fitted, was heavily corroded and in spite of lashings of WD40 , was very difficult to free up. In the process of holding the bolt head on the inside with a long nosed pliers, the two cables soldered onto the bolt head were unavoidably broken off. However , eventually it did come free. The cables will be re soldered to the bolt head , as found on reassembly.

With a complete clean up of the center bolt and the copper tab , this “STOP” button now works perfectly , following reassembly.

The copper “STOP” tab should be in sound electrical contact with he magneto housing ( ie fully grounded ) , while the “Live” bolt terminal is fully insulated from the magneto casing and the copper “STOP” tab by the pair of insulating plastic washers. When the engine is running, the center bolt terminal is “Live” , but once the grounded copper “STOP” tab is pressed firmly in, the “Live” bolt terminal center becomes grounded also and so the engine is stopped.

On reassembling, I will also add a cable internally at this point and feed back to the handlebars where a stop push button will be fitted, so allowing remote or emergency stopping of the engine , directly from the handlebars.

While the Wico Magneto specified is an A 576 BZ , the one fitted on mine is an A 1057 B Z. I don’t yet know what the significance of that is.

I took this opportunity to add a remote electrical stop , whereby I will place a push button stop on the handlebars, to allow remote engine stopping and emergency stops. This Magneto is fitted with two of the copper tab “STOP” buttons, one on either side of the magneto body. As I have access only to the outer side, I decided to sacrifice the inner one , and instead use that hole in the magneto body for the remote cable pass through.

I soldered the copper cable ends on both the brown and blue cables and then soldered the brown cable to the head of the live center bolt on remaining “Stop” I secured the blue cable to ground under the coil core clamp. A push button will be fitted on the other end of the cable at the handlebars. A cable tie secures the cable inside the magneto casing.

Based in York, UK , suppliers of Wico Magneto parts https://www.stationaryengineparts.com/Wico-Magneto-Spares/

Here is a website worth looking at. http://www.oldengine.org/members/diesel/Magnetos/MagData4.htm It does extensive coverage on the Wipac Type A magneto, including useful parts list and service manual pages.



Wico or Wipac

Company evolution

Wipac’s origins can be traced back well over 100 years to the start of the automotive industry: The Witherbee Igniter company (Wico) originally manufactured electrical components for agricultural machinery in Massachusetts as far back as 1892; they later became the Wico Electric Company, developing and manufacturing igniters in New York for the booming automotive industry in the early 1900s. In 1926 the Wico electric company started a servicing depot in London, which developed into a magneto manufacturing factory and in 1941 this division was purchased from the American owners by the Ministry of Aircraft production. In the late 1940s Wico was merged with the British spark plug manufacturer Pacy to become the Wico-Pacy sales corporation (based in Bletchley) and the Wipac brand was born. Over the subsequent years Wipac enjoyed great success in the design and manufacture of a huge range of mechanical and electrical products, the brand became especially well known throughout the UK for high quality car and motorbike accessories. By the 1990s the decline of the British automotive industry and increasing complexity of servicing modern cars had drastically reduced Wipac’s market and the Company needed a new business direction: In 1998 Wipac was purchased by Carclo and a programme of significant change and investment started with the clear objective to develop Wipac as a world-class Tier 1 automotive supplier, specialising in the high technology market of prestige vehicle lighting.