Erratic Tach reading

[GaryO]

91' Intruder 150. Starts and runs without any problems. Voltmeter shows just under 14 volts when running but the Tach is all over the place. After running for 15 minutes plus, it settles down and seems to be okay. Any thoughts or ideas to why it does this or when the problem might be? Drives me nuts!

 

[lmuss53]

Re: Erratic Tach reading

On my old Merc the same symptoms were caused by a loose wire on the ground block for the gauges. All the gauges grounded through one wire and where that wire hooked to the grounding block it was loose. I tightened that one nut and the tach never messed up again.