My 1979 R65?s tach had always worked well but its illumination light went out so I opened it up. The tracing of that circuit had blown. I repaired it. It blew again, and the tracing for Pin 6 as well. So I went through the whole motorcycle fixing questionable grounds and connections. Then I repaired the broken tracings again. Now all the lights work and circuits aren?t blowing. But the tach, when you turn the ignition on, goes to 4500 RPM and stays there rock solid until you turn the ignition off. Any thoughts?