Buddy has an 80" 1981 FXR with stock HD electronic ignition but no damn shop manual (now on order). There's no mechanical advance or VOES switch. I'm an old shovelhead guy and now have a blockhead so I'm wondering how they advance the timing? Is it done by reading the rpm's as a tachometer would? We're changing to new electronic ignition and adding a VOES for advance but I've never played with one of these. Thanks much. Dofiss

 

It advances by the rpm, just like points and every other electronic ignition do. The VOES just gives a signal to the ignition module to retard timing during low vaccum situations, same as a vacuum advance on a car.

 

I understand how a mechanical advance works as well as a VOES advance. This HD has neither which makes me ask how does it know the rpm's are increased?
I've been the sole mechanic on my HD's for 50 years now but am unfamiliar with this particular electronic system and how the advance works. My assumption is that this ignition advances by reading the RPM's directly to the electronic unit as opposed to a VOES or mechanical advance. We're adding a VOES for the new system but I mistakenly assumed it already had one being void of a mechanical advance, which proposed the question, how does it know?
Thanks for your response.