I installed a tach on my Sportster 883 Hugger, did all the wire splicing and soldering (had to cut the indicator lights, made sure to mark which pins were which, etc.). Now the bike won't start.

First few steps of the troubleshooting, it looks like I have a spark, albeit a weak one, on both spark plugs, but running through the checks in the service manual, it's telling me to replace the ignition coil.

I'm pretty sure the coil was working fine before I installed the tach, but I'm wondering if anyone can point me in a direction to test. I have a feeling I wired something wrong or broke something in the process. The coil has battery voltage, and like I said, there is a spark, but a weak one. There is fuel, too, because I can smell it.

I unhooked the tach from the plug, now the bike starts and runs. It runs with just the signal (pink) wire hooked up, but not with both the power and signal wire. It will run, but poorly, with the light bulb taken out of the tach, but the tach still doesn't register the RPM.

Somehow... the tach is drawing too much power, or the battery is too weak to use the tach. Or...some other electrical problem. Just need a place to start troubleshooting from here.

I would really appreciate some help. Thank you, Harley tech gurus.

 

Solved it.

The signal and power wire were flipped around. For some reason I read the voltage wrong on the pins. So it's all good now. Thanks everybody!

 

You're welcome, and we won't even charge you... this time.