Tachometer help, please

My tach decided to quit working this morning. It indicates zero RPM when the engine is off, and approx. 300 RPM (and steady) while running. All else seems normal. The tach worked fine when I parked the bike yesterday. Any thoughts?

Oh yeah, '82 XJ750J Maxim.

 

I'm assuming you have an electronic tach. Correct me if I'm in error. Shorted wire? Water/condensation in the connection? It's been decent weather this week so rain is not the issue. Wash the bike this past weekend? Just throwing out thoughts as they occur.

 

You have "Sticky Tach Syndrome." You can test to see how bad by lightly tapping on the instrument as you ride along. If it responds to the urging to "Get back in the game" after being tapped a few times; you'll need to lube its pivot gimbal.

The process involves removing the instrument from the inside of the panel.
Detaching the electrical leads from the rear of the instrument.
(Make a detailed sketch -- or -- take photographs.)

If you don't have a precision oiler ... this would be a good time to go buy one.
-Or-
Holding the instrument so that the rear of the instrument is level; apply 1 (One) drop of Marvel Mystery Oil -- or -- WD-40 to the small, brass pivot at the rear of the exposed bushing and bearing.
Use a TOOTHPICK to spread the drop along the Inside Diameter of the Bushing.

Use a clean toothpick to gently move the tach's indicator "needle" over beyond the red area to the stop ... then, release it and allow it to return to Zero.

Holding the tach so that you can see the front ... where the Needle is attached to the shaft ...

Angle the tack so that the shaft is angled "down-hill" ... and a drop of Marvel Mystery Oil wiped-on to the shaft ... off the tip of a toothpick ... will cause the drop to run down the shaft ... toward the inside of the instrument.

The trick ... is to bring the drop to the shaft ... with the tach positioned such that the drop ... won't drip on the face of the tach ... if the drop drips-off the toothpick ... before you get the drop wiped-on to the shaft.

See why having a precision oiler's going to make this whole deal a hell of a lot easier???

 

Robert, we had rain over the weekend and I washed the beastie on Monday. The odd thing is that I rode it to work on Tuesday and the tach worked. Delayed Condensation Syndrome? Maybe. I'm gonna try pulling the connections and drying the contacts before tearing the instrument cluster apart.

If I do have to resort to surgery I'll definitely buy a precision oiler. Big fingers + delicate work = mess.

Thanks, guys!

 

Weavalo,
How about trying a hair dryer when you you have the tach open to see if it has frozen water or a wet connection!?

Works well on watches that have condensatin on the bezel.
(says it's waterproof) Yeah RIGHT!

Rick is right on for lubing... wouldn't hurt if the hair drier works. Oil displaces water and will help keep it ut of those bushing next time.

Good Luck

 

We all need to be aware that low temps effect the behavior of the instruments ... particularly the tach.

Even a freshly-lubed, brand-new one might get a case of "The Lazy's" when ambient temps drop and close tolerances get even closer when they get the chills.

I'll be standing-by to see how the hair dryer attempt works-out.

Two cautions:
Don't melt anything.
Don't re-assemble it "warm" and expose it to low temps. You'll get condensation on the inside of the panel.

 

We're due for more rain this weekend so I'll try the hair dryer thing then. I'm a bit surprised that there's no condensation on the cluster lenses.

Sheesh. Just a bit of rain and something boogers. I can't imagine what would happen if I lived in a place that got real weather.

Thanks again for the suggestions.

 

You'd have to park it like most of us do.