Appreciated the help so much with my starting issue that I thought I'd try this one also....

I have an Acewell 2853 on my 1985 K100RT.  I'm using v.2 of Robmac's neutral light replacement card (which I seriously doubt has anytning to do with my issue).  All is well with this set up except that the tachometer acts strange.  It will jump up to way higher RPMs than are actually running.  Unscientifically, it seems to do it most when I'm decelerating and am letting off the throttle.  When I'm accellerating hard, it seems to register correctly.  Before I put the Acewell on, I didn't have any tacho issues with the OEM cluster.  I have the tacho wire hooked up to pin 16 from the OEM cluster, which is a blue/black wire.

Anybody have any idea what the problem is?  Would I do better to just wind the Acewell supplied wire around a spark plug lead to get a better signal?  Other ideas?  TIA.

The Acewell may not be rejecting noise on the input signal very well, causing false RPM readings.  Each trigger on the primary will cause ringing on the wire when the signal transitions (from low to high or visa versa).  I grab the same signal and feed it into my Motogadgets speedo without problems. The Motogadget is a much better gauge than the Acewell.

Winding a wire around the secondary as instructed in the Acewell instructions might give the gauge a better, cleaner signal.  Make sure to keep the windings adjacent to each other, and I think you might need to experiment with the number of windings.  More windings will result in a larger signal, however too many might overwhelm the input stage on the gauge.

The alternative might be to send the signal through a low-pass R-C filter to clean up the signal.

I had the exact same problem with my Dakota Digital instruments.  I put a noise filter in on the power that feeds the instruments and it fixed the problem.

Cheers.

Thanks guys. As I've already proven in this forum , I'm not good on electronics. Can you suggest a noise filter that I should use?

I would love to suggest one, but the one I am using is something my dad put together from re-purposed electronics he had around the house.