Speedometer/Tachometer Repair

Hi All,

I'm working on the gauges from a 1982 KZ440 with ~23k miles.



The needles on the gauges have always flicked around to some extent, the speedometer more so than the tachometer.  In the past few years, a whining noise has come from the speedometer in cold weather.  Now, the problem - unstable needle and screeching noise - has gotten so bad for BOTH gauges that I can't ignore it anymore.

I'm starting with the tachometer, because I think it will be simpler and less costly if I mess it up.  I've gotten to the point of having the trim ring peeled back so the gauge housing is apart, but I don't know what to do with the needle.  Most disassembly instructions I've seen/read indicate to just pop it off the gauge face with some spoons, but this needle is not coming off even with good force applied.  Can anyone confirm how the needle is supposed to be removed?  I don't want to break the gauge face trying to pop it off when there is another way to do it...

Once I had the needle removed, I'll be able to further disassemble it and take a better look at what is going on.  I've attached some photos showing some kind of debris, which I found to be non-magnetic.  At the moment, my inclination is that the problem is related to the play shown in the video.

The debris is probably hard to see:


Debris on my finger, non-magnetic:


Here is a video depicting the play I'm talking about:
www.youtube.com/shorts/rdoXrIiKy8w

Just out of interest, have you cleaned and oiled the drive cables before you pull the gauges apart ?

Just lube the input shaft with some oil. The play is no matter being the input shaft end is magnetic. 
Steve
 

I have cleaned and greased the speedo/tach cables recently.  I'm pretty sure its not the cable causing the noise as disconnecting them from the gauges causes the noise to cease.

I'm guessing that some lubrication might help with the noise, but I would like to get to the bottom of the unstable needle before I put the housing back together.  The debris I found inside the housing makes me think something is mechanically off and causing something internal to grind.

Might just be the picture you posted but the metal housing covering the magnet looks to be bent off level. This will mean the magnet rotating inside may be scraping on the inside face as it rotates. 
This would cause both the jumpy needle and noisy operation. 
Whilst you have it apart put a matchstick up the drive and spin it with your fingers, you may be able to narrow down the cause of the noise. 

I think the crooked appearance is just due to the picture.  I checked and everything appears aligned.

Now that I have everything apart, I can't replicate the noise or flicking needle when running the tachometer using a drill with square bit.  How annoying!  I would really like to find a potential cause to the problem before going to the trouble of buttoning up everything again.

If I could get the needle off, I could probably take apart the mechanism further and get a better look, but no luck on that front either.

I'll let you all know if I figure something out.

So the only difference between now and when it was playing up is the way your driving it. Drill versus cable. Kinda points to a cable issue as Steves first post suggested. Take the cable off the bike, fit it to the tacho then drive the cable with a drill and see if the issue returns. 

There is a clock spring holding the needle against the peg stop.  Before removing the needle, you might want to try to lift or bend the needle so it goes over the stop, then allow it to spring so you can see how much preload the spring has in its base setting.  Spring preload affects calibration, so it's not to be taken lightly.

I similarly took apart the gauges on my 750, to clean them up.  After the bike was put back in service, the needles on both units wobbled annoyingly.  There is a damping mechanism built into the device, but I never figured out how to service that.  In the end, I replace both gauges with NOS units, at considerable expense I might add.  And they don't properly match either.

... There is a damping mechanism built into the device, but I never figured out how to service that. ...

Possibly a fluid in the little can below the needle?  asphalt900 uses R/C car silicone diff fluid injected using a hypodermic needle syringe. I don't know if the can should have an orifice, but a pic of his shows the hole in the side of the can about 3/4 of the way up near the top.

I'll just add that sometimes an overly long inside cable can create problems you never imagined.  Are these cables original to the bike?  Years ago when mechanical gauges were still used in cars we would run into noisy or erratic needles on speedometers and we would just slightly shorten the cable first on the head side and then on the other.  By shorten I mean just a little bit, not a lot.  If shortening the inside cable seems to help but not eliminate the problem take a bit more off, but be careful, you don't want it too short.

Rick H. 

wrote:

Possibly a fluid in the little can below the needle?  asphalt900 uses R/C car silicone diff fluid injected using a hypodermic needle syringe. I don't know if the can has an orifice, but a pic of his shows the hole in the side of the can about 3/4 of the way up near the top.

I thought that I had read in the manual at some point in the past that the gauge needles are stabilized by a fluid inside the gauges and that inverting the gauges can cause the fluid to leak out causing the needle stability problem.  I'll have to check my notes to confirm the source...

I wonder why he uses silicon differential fluid.  I'll have to look through the threads to see if I can find anything more about it.

There might be a point on the cylinder positioned on the central shaft that I could inject a fluid into.  I'll have to check and get back on that.

The 750-4 chain drive FSM says to store them w the correct side up >> if left upside down or sideways for any length of time, a meter will malfunction.  As for the fluid, it's probably the closest thing he could find that was similar to the original stuff & I doubt anybody can say exactly what Kawasaki used. I don't know if the r/c fluid viscosity matters >> the FactoryTeam brand has quite a few choices.

original photo posted by asphalt900. edited to add text.