B21 Tachometer Bouncing

[BruceWard]

Above 2500 RPM or so the tachometer starts bouncing around and over reporting. It does not happen at lower rpms and calms down after a while. This started recently after sitting for a few months.

Any ideas?

 

[Carl_NH]

I rarely run my B21 above 2000 RPM, but sounds like a moisture / electronic issue. The tach is electronic not mechanical from what I recall.

 

[gwdixon]

Above 2500 RPM or so the tachometer starts bouncing around and over reporting. It does not happen at lower rpms and calms down after a while. This started recently after sitting for a few months.

Any ideas?

Check for a bad ground.

Try the battery ground first. Ground the battery directly to the engine block with a jumper cable. It happened on my L3650 with those tach symptoms..

 

[BruceWard]

Thanks I will check the ground.