Magneto question: Bosch ZR4 Dual

[jethro]

Just found this magneto in my parts accumulation. Although I've been fooling around with Model T's for years don't know much about this magneto. Please educate me.

R/S,
Jonathan Bodine

[John E. Guitar]

There’s a manual here.

https://michiganmotorcar.com/wp-content ... U4-ZR4.pdf

I’ve got the DU4 version on my P&L. It works well.

Your magneto looks like it’s missing some bits.

[frontyboy]

The Dual Bosch operated as a magneto and as a distributor for the Bosch dual coil ignition. A battery was used as an initial power sorce to cause the dual coil points to vibrate and then with the magneto distributor cover and plug wires send the spark thru the wires to the corresponding cylinders as the engine turned over.

So very basic, to start use the dual coil switch to fire one sparkplug at a time once the spark ignites that cylinder the engine should roll over to the next firing cylinder and so on until the engine is running then switch the dual coil to mag and the mag then takes over and the engine is now running on self generated magneto power.

I believe that distributor cap is incorrect. I think the correct cap should have a 5th terminal in the center of the cap which is connected to the dual coil switch.

just sayin'

brasscarguy

p/s, I believe I have an original Bosch dual coil instruction book if needed.

[jethro]

Thank you both for the education. Always interested in more info. Thanks again!

[John E. Guitar]

The distributor cap looks correct for the ZR4 Dual. There should be two connections on the other (input) end of the magneto. One of these is the "5th" terminal.