Speedo and Tach needle bounce

[Skinner]

1981 GS650GL, stock

So I removed the tach and speedo cables, cleaned out the housings, cleaned the cables, applied lithium grease and re-installed. Both cables looked just fine - no fraying or other damage. I expected as much because there is only 19000km on the bike. But the bounce is still there. I expect I'll need to lube both gauges, but how do I go about this? They look to be sealed so I don't know how I'd get inside to apply any lube. Suggestions?

I did a search this with all the terms I could think of, but all the threads that came up dealt with cable lubrication.

[Rob S.]

At about 70 mph, my tach needle is rock steady, but my speedo seems to vibrate.

Slower it seems steadier, faster I'm too busy to notice.

[Crankthat]

Somewhere there is a great thread or link on taking them apart.
I have done it and it worked great.

1 drill press.
1 Dremel cutoff wheel and shaft.
1 tube of crazy glue.

Insert shaft and cutoff wheel into drill press,.
Lay a piece of cardboard on drill press table just slightly bigger then gauge.
Place gauge glass down on cardboard.
Adjust press to desired height and lock in place.
Slowly make your way around plastic case with cutoff wheel by turning gauge.
Be sure not to go to deep.

Seal back up with crazy glue.

The few things I would have done different if I had thought ahead of time.

Three very small areas I would have left uncut and cut with a razor.
Just to keep original dimensions, they went together and fit in case great even though I did not do this.

Remove the small bolts holding on number plate and reattach with a pin tip drop of glue.
They have come out on a few sets of gauges I have.

Wipe the inside of glass with anti-fog wipe.
The set I use fog up and I did not know until after instillation.


I do not remember what was recommended for cleaning and lube of gears as that was not why I was inside them.

You could use another type of glue but with crazy glue a bit of nail polish remover (acetone) you can easily take them apart again.

Before you dig in some other members may chime in with important details I forgot.
Or possibly a better way of accomplishment.

[Brendan W]

I wouldn't go in there just yet. First off the only thing that could benefit is the input spindle and that can be oiled from the outside. The bezel that retains the glass can be prised off carefully and reformed to seal it up again if you really want to go exploring.
Two gauges at once would make me look at the mount rubbers after I had oiled the input spindles.
Is your s-bend brake hose pinching them by any chance ?

[Skinner]

I wouldn't go in there just yet. First off the only thing that could benefit is the input spindle and that can be oiled from the outside. The bezel that retains the glass can be prised off carefully and reformed to seal it up again if you really want to go exploring.
Two gauges at once would make me look at the mount rubbers after I had oiled the input spindles.
Is your s-bend brake hose pinching them by any chance ?

I'm going to try oiling the spindles from the exterior before I try to open them up. My brake hose isn't touching either cable. There are no sharp bend anywhere, just smooth curves from point A to B.

[Brendan W]

I'm going to try oiling the spindles from the exterior before I try to open them up. My brake hose isn't touching either cable. There are no sharp bend anywhere, just smooth curves from point A to B.

Just thinking that maybe the handlebar change had something to do with it.
What exactly is happening? Is it the needles buzz at certain speeds/revs or are they jumping through 10 degrees and do they do it together? Don't forget the mount rubbers.
I would expect a certain small amount of buzz at some speeds. Jumping is generally the cable repeatedly winding up and releasing due to friction in the cable itself or the instrument input spindles. Sometimes you will get a whirring noise with this, audible when riding.

[Skinner]

The bounce was happening before I changed the bars. I first noticed it after I installed my windshield. The cable are routed good - no bends, no kinks. I'm thinking it's just a 33 year old bike that needs a bit of lubrication. I'll take the gauges off this weekend and oil around the input spindle area.

The speedo bounces more than the tach, and they start at different times. They are both good at first, but after about 5 minutes of riding the speedo starts bouncing. The tach takes about 15 minutes to start and doesn't always bounce.

[Brendan W]

The bounce was happening before I changed the bars. I first noticed it after I installed my windshield. The cable are routed good - no bends, no kinks. I'm thinking it's just a 33 year old bike that needs a bit of lubrication. I'll take the gauges off this weekend and oil around the input spindle area.

The speedo bounces more than the tach, and they start at different times. They are both good at first, but after about 5 minutes of riding the speedo starts bouncing. The tach takes about 15 minutes to start and doesn't always bounce.

Long shot but, I'd be tempted, out of bone idle curiosity, to remove the shield and see what happens. As they shed vortexes ( almost sound like an expert now ) they can give a little flick and depending on how and where it's mounted...........
Lube is more likely though.

[Skinner]

Long shot but, I'd be tempted, out of bone idle curiosity, to remove the shield and see what happens. As they shed vortexes ( almost sound like an expert now ) they can give a little flick and depending on how and where it's mounted...........
Lube is more likely though.

You know, I considered the same longshot when I installed the windshield but not seriously enough to pursue it. However, last night when I was out for a ride the needles did not bounce - or at least bounced only very slightly - when I was heading east or west. When I turned to go south the speedometer needle was bouncing again. Then west again and it almost completely stopped, just a very slight movement. The windshield just may be the issue. I'm going to remove it and see what happens.

Its a Slipstreamer S-08 Sportshield for what it's worth.

[Brendan W]

You know, I considered the same longshot when I installed the windshield but not seriously enough to pursue it. However, last night when I was out for a ride the needles did not bounce - or at least bounced only very slightly - when I was heading east or west. When I turned to go south the speedometer needle was bouncing again. Then west again and it almost completely stopped, just a very slight movement. The windshield just may be the issue. I'm going to remove it and see what happens.

Its a Slipstreamer S-08 Sportshield for what it's worth.

Are you sure you're not looking at a pair of compasses?

[mrbill5491]

Does your bike have the magnetic drive speed and tach in the heads (there makes better sense now lol)? If they are there are two causes of the bounce, the magnet has gotten weak and/or the coiled spring has been compromised. Sometimes the bushings dry out though that would cause the needles to move very sluggishly if at all. Sometimes the bushings can be reoiled for them to work, though it has to be done at intervals after that. And if that is the case, start looking for replacements they can't really be fixed. This is assuming the cables are good and drive gears at their point of connection are good.

I've had the same problem with my 750 for years, I have 4 sets of both and only one set that I've been able to get working decent. Right now, I've been looking at SpeedHut's GPS speedo. Looks promising. As for the tach, probably will have to go electronic at some time.

[Skinner]

Are you sure you're not looking at a pair of compasses?

It would seem so!

I should have noted that the wind was coming out of west. With a tail or head wind the needles didn't bounce. With a crosswind the speedo needle bounced.

[Skinner]

Are these the magnetic driving speed and tach in the heads?

I have no idea. It's the stock instrument cluster for the 1981 650GL

[mrbill5491]

I have no idea. It's the stock instrument cluster for the 1981 650GL

Oops that should have said drive not driving. Any ways, take a look and see. May require some disassemblely to see it. If it is, what you'll see is a cone shape round magnet inside a barrel like thing connected to a coiled spring and then the indicator needle. The coiled spring you see is calibration for the tach and speedo respectively. Like I mentioned before if anyone of those two are bad, not much you can do to fix them.

[Skinner]

So I replaced both the tach and speedo cables with new. The tachometer bounce seems to be gone. And I thought the speedo bounce was gone as well. Before I bought the new cables I removed both gauges and oiled them both with a very light mineral oil. This did nothing to relieve the bouncing. I then bought the new cables, installed and went for a ride. The gauges were performing very well, but after about 5 miles the speedo started to move a bit and within a few more miles was bouncing again, albeit not as much as with the old cable. So, any thoughts? I'm perplexed because the speedo does not bounce right away. I assume my next step is to disassemble the speedo and see what's happening inside.