tach weirdness number 27

[andyoutandabout]

Spent time reading past tach problems like reading double, not reading at all and bouncing all over the place.
My new meter reads low. It kinda looks like it's suffering from power starvation. Does not bounce, sits pleasantly at tickover, picks up smoothly but slowly and reads something like 4,000 at 70 in top gear (about 1000 rpm less than it should with my 18/44 gearing according to the files gearing tables).
I'm all in bits at the moment so this is a really good time to have a solve.
I will clean contacts as recommended.
I've tested the grey wire for continuity and it's good.
I'll clean the grounds......
Anything else while she's in dry dock?

[ren-dog]

Hey andyoutandabout,

I am reading that your tacho is low all the time?  So I got to thinking  (yeah I know I shouldn't)

Possible issues;
Earth problem,
Half broken signal wire, (but this would only show up when hot)
Too high a resitance, (dirty contacts or corrossion in copper wire)
Alternator output low, (<13.8 Volts)
Faulty coil, (bike would be down on power too)
Sticky gucky stuff inside tacho mechanism.

Hope you find the problem

[Pat Conlon]

Andy, you mentioned that you checked continuity, but did you check the wire's ohm's resistance with a multimeter? If you suspect a voltage issue, it will show up as a higher than normal ohm reading on the suspect wire.

[DaveA]

I've just gone through the same with my bike, and managed to fix it.  I took out the instrument panel, cleaned all the points with some sand paper and the rev counter is now working perfectly

[andyoutandabout]

Bike back in one piece awaiting weekend testing. A good cleaning of all contacts with our eternal friend WD40 will be on trial as tach readings are duly noted.

[Klavdy]

Tight Arse, have you bought a new battery yet?

[andyoutandabout]

The combo of new battery (yes Wallyworld had one on the shelf for $40) and a good WDing of contacts seems to have improved tach matters no end.
However, when the moon enters a new phase, I could easily be back to square one. One wonders if Fj gauges were built by Ducati.