Need Help w/ Bosch Mag System

[jquam]

Does anyone have an electrical schematic or hands on knowledge of a Bosch DU4 Duplex Model 4A with a Bosch Duplex coil switch. Terminals on the switch are Bat+, Bat-,

Mag 1, Mag 2. The wiring seems straight forward, however, I'm not sure how the switch works in the Battery position

The switch is 3 position: O (off), B (battery), M (mag) plus a push button in the switch handle.

The application is a 1914 Kissel Kar semi-racer

Thanks

John

[Mark Shaw]

John,

I have a Delco ignition switch & run a Bosch Du4 Magneto on my 13 Buick. The Batt position on the switch is used to start the car on battery spark for hand cranking (or while using the acetylene starting system on my car). Once the car starts, you flip the ignition switch over to Mag to run the car.

I belive the battery position is intended to provide a stronger spark for starting than a magneto without an impulse coupler.

[jquam]

Thanks for the reply Mark

I know the procedure of starting on battery for a stronger spark on initial starting and then switching to mag, however, on my Bosch ignition switch there is a pushbutton built into the switch lever and I was wondering if this needs to be depressed when starting on battery. A schematic would be very helpful to see how the switch functions.

Thanks again for the help!!

John

[21raceabout]

The button on the center of the switch is the "ignition"; when you put the switch to "battery" and push the button, it sends current to all the spark plugs at once. The cylinder which is in the compression part of the stroke, if it still has compression, will fire and start the engine, if you are lucky. This will save you from needing to hand crank start the car. If it is working properly you should hear a "growling" sound out of the switch when you push down the button. If the engine doesn't immediately fire after holding down the button for a only a second or two, get out the hand crank. This is not an electric starter switch so repeatedly pushing the button without doing anything else will not work. Obviously you only push the button with the car out of gear and the clutch depressed. The "ignition" switch starts my 1911 White only about 1 in 20 tries, usually only when it's hot. Thus my normal starting routine is to "tickle" the carb (lift the float until gas starts to drip), put the switch on "battery" (without pushing the ignition button), retard the spark, throttle 1/2 open, OEM compression release open and she will usually start on the first pull. Immediately close the compression release, advance the spark about 1/2 way, and switch to magneto.

[jquam]

21raceabout

Thanks very much for the information, I really appreciate it!!

Regards

John