Speedo and Tach needle bounce

[William Groebe]

ideas

Skinner.

I've had similar bouncing needle problems with tach and speedo on my 1982 GS650GL. Both tach and speedo are the magnet speedcup kind.

In the case of the speedo the speedcup had broken off of the needle post, so as the speedcup was spun by the magnet it would only sometimes catch the post to turn the needle. I tried using JB weld on the connection point, but after a few days it came loose and the speedcup got all shredded up on the sides of the speedo frame and is now completely destroyed. If I were to do it again I may try a bonding agent that is more flexible than JB weld. I documented the process here. http://preview.tinyurl.com/nywa6u4

In the case of my tach, the weld point is weak between the shaft holding the bar with the spinning magnet. It's almost as if the connection point got corroded over the years. I've yet to fix my spinning tach needle as I haven't got around attempting to weld it fixed.

Good luck.

-Will

[jbthomp]

I ran a little marvel mystery oil down the speedo cable on mine and it worked a whole lot better.

[WilliamGLX81]

Nope. There is a set of bearings that the spring/magnet counterdrive/drive ride on. They need to be lubed with sewing machine oil while moving the gauge back and forth.
The cables and input port aren't the problem.

[Skinner]

Just to add fuel to the fire about the windshield causing the problem...

I was riding east at about 90kph and, as per usual, the needles weren't bouncing for the first 5 minutes or so. The speedometer then started it's usual little dance. What's interesting is what happened when an approaching car would go past in the other lane. Each time a car went by there was a blast of air and the speedo needle would take a big jump, then settle back down to it's "normal" bounce. This happened for each vehicle that went past until I turned off that road and headed south (cross wind). Now when a car would go past there was no blast of air and the needle didn't make it's big jump. I then turned east again and the same thing happened with passing cars - big jump.

This leads me to believe that there is something to the theory of the windshield causing this problem. I've lubed the gauges and replaced the cables, so I'm now going to remove the windshield and see what happens. If that is indeed the problem then I'll have to come up with some sort of a fix.

I'll report back with my findings.