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Crazy Speedometer

EASTER85

Robert E
I have a 1978 R80/7 that I have had since new.... I have noticed lately that on the highway at highway speeds the speedometer needle will start to gain speed. It will eventually go all the way up to 140 mph. The "odometer" is working normally even when the speedometer needle is smoothly hovering over towards 140 mph.

It is not erratic like the cable is binding. It is more like the speedometer is getting to much voltage. This only happens after you have been riding on the highway a while. It acts normal around town.

I was wondering if a part is failing; or, it I might have a bad ground??? Any ideas???
 
The speedo is driven from the transmission through the cable mechanicley not electricley.

.First replace the cable to see if it helps, if not, speedo may need a rebuild.

good luck!
 
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I don't think it is the cable as everything is very smooth. In the past I have had speedo cables that went bad... This one acts like something is going on in the speedo head.

If someone has had this experience before maybe they can tell me what is going on. Otherwise I will contact a speedo repair shop... There is one near here in Austin; and one in California.

Thanks.
 
99% chance that it is the speedometer itself......Before it begins to self-destruct get to the ol boy over in Austin......Good guy, honest, and a craftsman......You could try taking the instrument out and spraying the workings with some SILICONE spray and try it; but mostly it probably just needs a good cleaning and lube before it does the sooner or later needle bounce and screaming mode...................God bless and good luck.......Dennis
 
Thanks Dennis... I used him to calibrate the speedometer many years ago. He is a very nice guy... I will give him a call.
 
Over time the cable goes bad and it creates a vibration that will tear the speed cup apart on the back side of the speedo. Take the cable off at the back side of the speedo and spray something like WD40 down the speedo cable and see if that helps a little bit. If it does it's your cable.

When and if you have the speedo rebuilt make sure to buy a new cable.
 
I sent my speedo to Austin several years ago for repair. He did a good job at a relatively reasonable price and the turnaround was fairly quick. The one in California was considerably more expensive (more than new).
 
Click on the Resources and Links thread in my sig line and find the section on speedometer repair. The guy from Oregon is in that list...known at Wirespokes. Not suggesting he's the way to go, but several resources are there.
 
Thanks for all of the good advice from all you guys. After looking at the links the next thing I will do is get on the phone...
 
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