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Gadget Freak Case #235: Ignition Control Unit for Harley Davidson Panhead Engine

Edward Nauman designed an ignition control unit for the Harley Davidson Panhead engine. The unit can be adapted to almost any four-cycle engine with the proper design and fabrication resources.

One of my riding partners rides a 1957 Harley FLH (Panhead) that runs on gasoline. It is a classic motorcycle with the look and feel of what real adventure riding is all about -- the epitome of the outlaw biker style.

Part of the experience of riding a Panhead comes from the era before motorcycles had electric starters. Kick-starting a big twin Harley engine isn't hard if you know what you are doing. If you don't do it with the right technique and respect, she might throw you over the handlebars. I know a lot of Panhead owners who swear their motor starts on the first kick, which is probably true for the most part. But they will also tell you everything must be just right for it to come off on the first kick. I've also watched a few guys kick until they were blue in the face when things weren't just right.

The main driver for doing this project was to educate myself on the intricacies of starting the big twin engine with your foot instead of your thumb. The secondary motivation was to see if I could design an ignition system that would enhance the performance.

The ignition control unit (ICU) was designed from the ground up. It is based on an Avago quadrature encoder with 1,000 pulses per revolution. Because the encoder mounting requirements dictate fairly precise mechanical location and stability, it was necessary to machine a whole new housing and drive shaft, rather than using the stock parts. The housing is machined out of 6061-T6 aluminum billet and carries four precision sealed roller bearings to support the drive shaft. The drive shaft is machined from 304 stainless steel.

The stock helical drive gear was utilized with an added miniature precision thrust bearing, instead of the stock thrust washer. There are locating pips machined into the encoder mounting flange, which takes care of aligning the encoder head. The matching code wheel is also stainless steel for survivability. The electronics are contained on a single printed circuit board mounted above the encoder. The assembly is protected by a screw-on cover machined from billet aluminum.

Click the image below for more photos of the ignition control unit.

Edward Nauman designed an ignition control unit for the Harley Davidson Panhead Engine from the ground up.

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