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Bouncing Speedo

  • Thread starter Thread starter KPottorff
  • Start date Start date
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KPottorff

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Anyone have a suggestion for a speedometer that works fine at lower speeds (for the most part) but begins bouncing from 10 MPH to 60MPH at highway speeds?
I've gone through the how-to for working on the instruments with the plastic cases, but I've got a '78 GS400 where the cases for the instruments are steel. I don't want to go prying up the metal retainers for the glass so that I can get inside. I know from previous experience with my old air-cooled VWs that they never go back on as tight as when they came out of the factory.
I used a little lube in the input shaft portion of the speedometer but I don't want to just go spraying around inside where I can't see the mechanism. I also cleaned and lubed the cable - feels smooth when I turn it. And as far as I can tell, the drive in the hub is working OK.
 
Last edited:
Zen Budist Speedo Master Required

Zen Budist Speedo Master Required

I've heard that most speedo's are not really servicable. If you can get into it you probably need some pretty obscure info on what to clean and lube it with. A used one is probably your best bet. Keep the old one and record the milage on the replacement on it when its installed so you can calculate the actual mileage on the bike. Short of that check the yellow page or do a Google search for a repair shop. Mine gets a little wierd now and then so I just use the tach to get the mph.
 
How is your cable routing. Sharp bends, particularly those that reverse direction such as "S" type will cause a problem

Earl


KPottorff said:
Anyone have a suggestion for a speedometer that works fine at lower speeds (for the most part) but begins bouncing from 10 MPH to 60MPH at highway speeds?
I've gone through the how-to for working on the instruments with the plastic cases, but I've got a '78 GS400 where the cases for the instruments are steel. I don't want to go prying up the metal retainers for the glass so that I can get inside. I know from previous experience with my old air-cooled VWs that they never go back on as tight as when they came out of the factory.
I used a little lube in the input shaft portion of the speedometer but I don't want to just go spraying around inside where I can't see the mechanism. I also cleaned and lubed the cable - feels smooth when I turn it. And as far as I can tell, the drive in the hub is working OK.
Click to expand...
 
I've not done this before, but had it recommended for a bouncing tach (on the 750). Disconnect the cable from the speedo housing and the hub. Then try and remove the innards of the cable. Take some WD-40, or similar detergent oil, and spray it liberally into the cable housing. Also try and wipe the cable clean. Replace the innards after lubing with some grease (white lithium should be okay) and reconnect the cable. From what I was told, the cable can bind, causing the bounce. Just my $.02.:)

Brad tt
 
I had a much less severe case of this problem recently and I found that the WD-40/wipe/lube process helped a little but did not eliminate the problem. One thing to check is that the cable endpoints are tight. When cable starts to deteriorate, those endpoints may loosen up and allow the cable to slip, especially at high RPMs. I had this happen to my tach. It would bounce around at high speeds too. Eventually it just let go all the way. Problem went away entirely with a new cable.

If you do wind up getting another speedometer.. maybe you can experiment with the old one: try drilling a hole in the case and squirt some graphite powder in. If you find something that works, let us know :)
 
DimitriT said:
I had a much less severe case of this problem recently and I found that the WD-40/wipe/lube process helped a little but did not eliminate the problem. One thing to check is that the cable endpoints are tight. When cable starts to deteriorate, those endpoints may loosen up and allow the cable to slip, especially at high RPMs. I had this happen to my tach. It would bounce around at high speeds too. Eventually it just let go all the way. Problem went away entirely with a new cable.

If you do wind up getting another speedometer.. maybe you can experiment with the old one: try drilling a hole in the case and squirt some graphite powder in. If you find something that works, let us know :)
Click to expand...

Replacing the cable would be second suggestion, also. Less work, but more $. Not sure what they go for new.:-D
 
KPottorff said:
Anyone have a suggestion for a speedometer that works fine at lower speeds (for the most part) but begins bouncing from 10 MPH to 60MPH at highway speeds?
I've gone through the how-to for working on the instruments with the plastic cases, but I've got a '78 GS400 where the cases for the instruments are steel. I don't want to go prying up the metal retainers for the glass so that I can get inside. I know from previous experience with my old air-cooled VWs that they never go back on as tight as when they came out of the factory.
I used a little lube in the input shaft portion of the speedometer but I don't want to just go spraying around inside where I can't see the mechanism. I also cleaned and lubed the cable - feels smooth when I turn it. And as far as I can tell, the drive in the hub is working OK.
Click to expand...

I have had the same symptoms with different problems each time.

first time the speedo needed oil, it was not turning free. Second time the bottom of the cable had nearly sheared off and was not turning freely. Third time the speedo cable came loose on the back of the speedo itself.
 
For all who threw in their two cents worth:
The routing of the cable is OK - can't get into too much trouble between the hub and the back of the speedo.
I pulled out the cable from its sheath and worked it over. Used some 30W oil to lube it. It doesn't need much.
The cable ends looked OK - solid attachment to the cable, squared off with sharp corners going into the hub and looking like a fork on the head end. I don't feel any binding in the sheath when I turn it by hand.

If it comes down to it, I'll go the cheap route first and get another cable. But I suppose I'll live with it for now. It's turned out to be a good bike even though it is nearly 30 years old. A lot better than a '73 Honda 450 I had some 25 years ago - that thing ate two sets of pistons even though it wasn't abused. Well, not much...
 
Before you do any surgery on your speedometer or buy a new cable, try removing the whole cable assembly, pulling the inner cable out and flushing the cable housing with something like WD-40. Use some to clean the cable too.

Before lubing the cable, check to make sure the drive ends are securely fastened to the cable. Sometimes they loosen and will spin on the cable causing the symptoms you describe. If it's loose, try some good old JB Weld to fix it. I did this to my tach 3,600 miles ago, and it's still working fine. Be sure to thoroughly degrease the parts before you apply the JB Weld.

While you're at it, pull the speedo, flip it over and apply some fairly lightweight oil into the opening for the cable end. Not too much so you don't get oil all over the inside of the gauge. :?

Apply some good cable lube, reassemble everything and see if this cures your problem. This is how I fixed my tach, and it was doing the same thing. It's a cheap fix, and worth a try. :wink:
 
since you have already taken care of the cable, you have one other option:
do something with the head itself.

The glass top has a metal surround bezel, and it can be pried loose.

Exercise care to avoid breaking the glass. That said, I used a pair of pliers.

Your problem is almost certainly the mount inside the housing where the cable enters. There is a magnet and gear section in a fragile mount. The magnet spins in relation to the speed of the cable and the moving magnetic field deflects the needle. Over time it comes loose......just a bit....but that is enough to allow the needle to move off centre, then catch inside the housing, and when that happens you see the twitch.


Repair is touchy, as you have to properly centre the piece, then stabilize it, and it is tiny, so you have very little to work with.

I never did fix mine, as I could easily see the wear from so much twitching over a long time had worn away the surface areas. I had a spare, so I did not waste more time on it.
 
I've had similar problems in old cars. I fixed them by (1) cleaning and lubing the cable; (2) replacing the cable and housing it #1 didn't work; (3) replacing a plastic gear in the transmission if #2 didn't work.

Cable lube is different from white grease - it runs dry.

And good luck if your problem is in the speedometer head. I've had a couple of those repaired, and it was about $200 each time. If it came to that, I'd look instead at a bicycle speedometer.

Tom
 
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