I have a 2015 Raider Bullet Cowl that I recently installed a Barons Black Tachometer w/Black Face - BA-7570-01 on (Dennis Kirk Part #: 4000078).
I installed the Barrons single fire tach adapter that came with the tach as directed. All connections are soldered, and the ground goes back to chassis ground.
It looks really nice, but I had really bad needle bounce. I contacted Barrons support via email. They gave me a few ideas, but they were unable to help get rid of the needle bounce.
I found someone on a forum who had a different model tach, and had needle bounce. They installed a Split second TA2-100 Tach adapter. I installed one on my bike and now the needle bounce is gone...steady and responsive.
The Split Second Tach adapter TA2-100 will work with any tachometer, bike, car, or any engine that uses a coil to spark plug for engine combustion.
Web site
https://splitsec.com/product/ta2-100-tach-adapterYeah I really didn't want to spend an extra $100, but it's worth it to get rid of the annoying needle bounce.