Rev Counter jumps around 6000rpm

Hi all,
Have my 82 XJ650 starting on the button now mainly due to the great advice I have been given here by all you guys.
Here's something I noticed yesterday though.
Hadn't started her in over a week.. Had been lashing rain for at least a week so didn't bother. Yesterday she fired up first go and I took her for a spin.. But I noticed if I pushed her to 6000 through the gears that the needle jumped on the tacho.
I cant say I noticed any misfire or loss of power though and it doesn't do it when you rev her up in neutral.
Any ideas.?
Thank you all.
Morgan.

 

A sketchy connection could increase the pulse count on an electric tach.
The tach displays what it thinks the engine is doing.

 

yeah, i'd just take the connection apart, hit it with some contact cleaner, then put a bit of dielectric grease in the connectors and see if the issue goes away.

 

Dont let the yarn ball in the headlight bucket scare you

 

Depending upon where you are, ... the Tach might be erratic do to the cold weather.
In the late Fall and early Winter, ... the Tachs on both my 750 and 900 become virtually useless.

You might try cleaning the Tachs Bearing Bushing.
Open the Tach.
Clean the Pivot with a few drops of Isoprophyl Alcohol.
Move the Indicator Needle through its arc very carefully a few times as the Alcohol dries.
Then, lube the Bearing-bushing.
Apply two drops of Sewing-machine Oil to the Bushing.

Or, 3-in-1 Oil.
Dip the tip of a Toothpick in a Bottle-cap's worth of 3-in-1.
Spread two drops on the Bearing.

 

Where would I be without all of ye...On the side of the road most likely.
Thanks for all the advice..It could have been just the cold cos it doesnt seem to be doing it now.