Guage dilemma
 

So I am installing an aftermarket dash. The speedo uses a sensor on the front wheel but the tacho I plugged into the stock harness. It reads ok up to like 4k rpm but beyond that goes to zero.

I have experimented with the winding around the spark plug wire method but it didnt seem to work well.

Has anyone done it a different way & had success?

Does it seem accurate up to 4K or when the bike is at 8K or 2K it reads 4K?

It is accurate to 4k but if you rev beyond 4 it goes to zero on the guage. (which is how I initially worded it)