Motorcycle Repair: 2005 Harley Sportster 1200 HL, harley sportster 1200, fire ignition

Question
QUESTION: Trying to hook-up an aftermarket tachometer. Which is the negative connector on the coil? *It has three prongs*. My tachometer wires are Ground, neg tach wire, light and power. The ignition system is stock, which I assume is a dual fire ignition.

ANSWER: If you have 3 posts on the tac then you have a single fire ignition. One is hot and the other two go to each plug, so you will need a tac for a single fire ignition.
Good luck and happy riding
Mike

---------- FOLLOW-UP ----------

QUESTION: Do you mean, if I have 3 posts on the coil (not the tach) on the bike, I have a single fire ignition? If so, then I have to get an adapter for a single fire ignition system to make the tach work. Also, I assume I can use either of the two negative posts, how do I tell which is neg and which is pos,,,,thanx for the help

Answer
One quick way to tell if you have single fire. First, locate the positive wire with a test light. It will be the continuce hot one. You will probably have to take the wires off to find it. Now connect one of the other wires and with the plugs out turn the bike over and check each plug for spark. If only one sparks, then you have single fire.
If you do have single fire then you sill have to get a single fire adapter.
Good luck and happy riding
Mike