I got the info for the adapter from Gadget's Vulcan page. There are several other threads about it on this board. The Gadgets page has a good how to article with a schematic and parts list. In my case which I am not sure is true for every tach, I had to reverse the direction of flow for the diodes from what is shown on the diagram, to make them work. Yes the Vulcan 900 is a "single fire" engine. That means there is just one ignition spark for each cylinder, during each 4 stroke cycle. Some of the Harleys in paticular use a "dual fire" or "wasted spark" ignition system, where there are 2 ignition sparks during each 4 stroke cycle. (If you don't use the adapter with a Harley tach on a Vulcan 900 the tach will read half the RPM's the engine is actually turning.)
2006 VN900 Classic LT
Last edited by ikindoit; 04-22-2010 at 02:00 PM.