Inaccurate Tachometer


Information and questions on GL1200 Goldwings (1984-1987)
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garywyoung
Posts: 27
Joined: Tue Sep 20, 2016 7:32 pm
Location: Cincinnati, OH
Motorcycle: 1982 GL1100

Inaccurate Tachometer

Post by garywyoung »



Howdy--I've searched for a similar problem here but haven't found one posted: my tachometer is wildly inaccurate, showing excessive RPMs (7k+) when I know the engine is probably running at 3k max. At higher engine RPMs (5k+), the tachometer will max out, then drop to what is likely an accurate measure (5k or so), but one I back off the throttle to something like 3-4K, the tachometer goes back to reading crazy high numbers. At idle it's accurate, but just the slightest amount of throttle shoots the needle to the high numbers again. FYI, this is an 84 Interstate without the LED gauges.

Any theories? Any suggestions?



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julimike54
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Joined: Sun Feb 01, 2015 12:21 pm
Location: Euless, Texas
Motorcycle: 1986 GL1200A original owner
2016 HD FLTRU

Re: Inaccurate Tachometer

Post by julimike54 »

Possibly a bad electrical connection from the coils to the tach. Follow the wires and clean/check all connections for corrosion, same for the ground circuit. If not it will be the meter that's the problem. I think that circuit goes through the 'Kill' switch, and may have to clean its connections also. That's my suggestion.
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virgilmobile
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Re: Inaccurate Tachometer

Post by virgilmobile »

The tach needs 3 electrical connections.12 volts,ground and the pulse wire from one coil primary.
I would suggest augmenting the ground wire first.Just hang a wire from the meter to the battery ground post then test.
Second..hang a wire from the 12 volt connection to the battery positive post then test.If neither resolves the problem,remove the tach and get into its electronics.The ignition pulses are coupled to its innards through a few resistors and an electrolytic capacitor. The cap is my first suspected part.

garywyoung
Posts: 27
Joined: Tue Sep 20, 2016 7:32 pm
Location: Cincinnati, OH
Motorcycle: 1982 GL1100

Re: Inaccurate Tachometer

Post by garywyoung »

Excellent! That's exactly the info that I needed! I'll report back on my findings. Thanks!



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