Speedometer Head

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    • The speedometer head is what registers speed, total miles ridden, and a resettable or trip odometer to show miles since last reset. As such, the head is rather complex in its inner workings. A complete discussion of repair is beyond the scope of this writer and the purpose of this post.
    • There are several areas that seem to be a reoccurring question. One is: How do I get inside the case? There are only two options that I am familiar with. One is to uncrimp the chrome band between the halves. You only have to do one side, generally the back is done to minimize visual effects on the bike. This involves using a small screwdriver or other tool to continually go around the crimp until it is open enough to remove the back half. This is much more difficult than what it sounds like, in that the crimp is very tough to pry up and eventually the blood from all your puncture wounds will cover the seam. Cursing has also been tried an it doesn't seem to be of any benefit. It can be done if you are patience enough and the advantage is that the repair is almost unnoticeable when the head is re-installed.
    • The second way us to use a Dremel tool with a thin cutting disc to slice through the band at the bottom of the head. A jeweler's saw or thin hacksaw will also work if you are careful. Once the band is separated, the halves can be opened up and removed. The top half should be able to be rotated in such a manner that the odometer reset knob can pass through 'the hole in the case half. You may have to remove the rubber boot first to allow the knob to pass through'. With the top removed, the inner workings are held in the bottom half by two screws on the back. This should allow you to completely remove the inner cluster. When it is time to put the case back together, the easiest way is to drill a small hole close to each end of the cut part of the band, and use a SS twist tie to cinch the bank back.
    • The now exposed parts can be serviced. If the unit was working before you opened it up, you may only want to insure the two face holding screws are snug, and oil any of the bearing points. Since this is similar to a clock, I use a clock oiler that contains a special oil. These should be available on-line and have long, almost hypodermic end on a squeeze tube. This allows you to place a micro drop on tiny bearings to avoid oil running everywhere. Also oil the inside of the drive coming into the head. This is a common area for squeaks to develop. Another thing to check are that the two magnetic hemispheres do not have any grease on them which may cause them to bind with each other.
    • A real CAUTION is to not use a spray type carb cleaner around the inside of these heads. Any contact with the cleaner and the face or mile numbers will cause the numbers to melt off. A Q-tip with cleaner is much safer to remove old grease and oil.

Here is a forum post by Deanbw on his experience with cleaning a tach head:

Ok, so I had a gauge (tach) that was slow, so I bought one for cheap, it too was slow, in fact it was sticking. I thought well I have two so lets see how this goes. with a small good screwdriver you can catch the edge of the crimp ring from the back and pry it open. just work your way around the gauge slowly going about half the width of the blade at a time. once you get about 3/4 of the way around you can slide it apart. Then I wipe it out with a q-tip, spray it good with a light lube ( I've used wd40 or kroil) then I hold the needle with a finger and blow it out with air. It gets rid of the excess oil and gets it into those hard to reach bearing areas.Then I wipe clean the face with the same lube, it acts like a mild solvent, cleans off the oxidized surface without taking the black or red paint off. Now to re-crimp the ring you have to be careful so you don't dent the front, and you have to press the two halves together hard enough to let the rubber gasket seal again, hard to do and not hurt the ring with a pair of channel locks and impossible by hand. I took a piece of uhmw and some scrap angle I had and made a tool for holding the gauge, then I work my way around with a small flat nose punch and a small hammer, take your time working it back over the edge in steps, about an inch at a time. first get the bend started about 45deg. then about half that again then all the way down, this makes it stay equal around the gauge and doesn't crease the back of the ring. works good here's a few pics to give you the general idea. Resized to 83% (was 640 x 397) - Click image to enlarge gaugeapart_zpse1cd1c9a.jpg Resized to 83% (was 640 x 480) - Click image to enlarge gaugehalf_zps6142be7a.jpg


Resized to 83% (was 640 x 480) - Click image to enlarge gaugetool_zps9cdf37b4.jpg


Now the problem with doing this is when you put the gauge back on the bike, the other one you thought was clean... looks like crap, now I have to take the other one apart or it's going to drive me nuts looking at that. Resized to 83% (was 640 x 480) - Click image to enlarge speedotach_zps69801d19.jpg

    • Here is another thought on removing and re-installing the chrome band, by Hughmoth:
    • I'm not that patient. My method is to cut the stainless steel band with a abrasive cut off wheel on a Dremel tool. To re install I drill a tiny hole in each end of the band, string a piece of stainless steel safety wire through the holes and twist the wire until the band is tight.

There has been some discussion as to how to reset the mileage on these speedometers. Also on how to remove the number face. Both of these are addressed in the following writeup and pictures by LRCXed.

    • There has been a bit of talk on resetting a speedometers odometer to zero again or any other mileage setting your looking for. So since I'm resetting one to 00000 for a CX 500 D that I'm building, I thought I might as well take pictures of the steps it takes and post them here for you all to refer to. The speedometer I'm doing is from the custom style with the separate gauges. The same process works for the Std. style as well. But it's a lot more difficult to reassemble the two halves of the Std. style gauges than it is to do the type I'm showing here.
    • OK, here's the specimen I'm resetting. The chrome band that connects the two halves needs to be cut to get the assembly apart. I've seen people pry up around the back side of the ring to get them off but I prefer this method. It looks much cleaner in the end. I'm using a Foredom with a flex shaft that has a very thin cutting wheel on it to cut the band. But there are other ways to cut the bands.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1400.jpg

    • With the band cut you will need to use a thin knife or scrapper to pry the two halves apart. Be patient and don't force it too hard. These have been pressed together for 30 years plus and need to be coaxed slowly.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1401.jpg

    • After the two halves are apart you need to take out the two screws that hold the main unit into the back half. Sorry I forgot to take that picture. But the screws are next to the drive unit that the cable goes in.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1402.jpg

    • Now you need to remove the screws that hold the face plate on. Be careful not to slip. The face is plastic and you don't want to break it.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1403.jpg

    • Now comes the tricky part. Getting the needle off. They are pressed on pretty tightly usually. If you try to pry it off between the plastic face and the needle you take a chance of marking things up or breaking the needle. What I do is to put a screwdriver UNDER the plastic face plate just under the needle and twist it to pop off the needle. Be careful where you place the screwdriver though. You don't want to pry against any plastic parts like the rollers with the numbers on them.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1404.jpg

    • Now on the side you'll see a copper clip holding a spring and plastic collar in place. Push this off with the edge of a flat screwdriver.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1407.jpg

    • Here is what the clip looks like.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1408.jpg

    • Next you'll see the second clip that holds the numbered rollers together tightly. Take this clip out too.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1409.jpg

    • Now is where you can reset the rollers to the numbers you choose. Start from the left side by sliding the roller to the left. This disengages the gearing in them and allows you to roll it. Be gentle. They tend to want to catch as you turn them if they are not pushed totally away from the adjoining roller next to it. When you get the one moved to the number you want, slide the next one over and rotate it to what you want. This is done with each roller one at a time from left to right.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1410.jpg

    • When you are done with all of them you will end up with a gap between the tenth number roller. This one is engaged to a metal gear and isn't worth trying to move.
    • Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1411.jpg

    • Now you can reverse the clip removal steps and put it all back together. When I'm done I always test the unit with a drill driven in reverse to make sure it all works for a mile or two. The millage put on by testing can be reset to zero by running the drill forward before you put the needle and face back on.

A word of warning! Be careful when you are pushing the clips off. Pressing it down on the bench like I did will break the alignment tabs for the trip meter. I'm lucky that this won't effect the unit from working since the actual lock is up against the metal plate of the assembly. These pieces are used on both sides of the speedometer. So I got lucky that it's not going to effect the function of the speedometer or the trip monitor. Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1413.jpg

With the unit and face plate screwed back in the next step is to set the needle in place. I use a drill with a section of cable that I use to drive the speedometer or tach before I take them apart. The speed is just under 35mph usually. So I set the needle on the stem very lightly and run it up to see what it's sitting at at that time. If it needs to be adjusted I can move the needle down or up depending on the need. This one needed to go down. So I put the needle on the underside of the peg and pressed it lightly so I could move it to the other side and test it. When it's at the correct setting I just simply press down harder so it will stay permanent. Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1415.jpg

Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1416.jpg

After the glass inside is cleaned and I dab a tiny bit of oil on the bushing that the needle rides on as well as the inside of the input shaft, It's time to put the top back on and assemble it. Since I used the cutoff wheel to cut the band off I simply line up the cut marks to get it back in position. Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1418.jpg

When cutting the band off you'll find that they expand a bit. I gently roll the band with my fingers to get the gap to close up. That way there is no outward tension trying to open it back up after it is glued back on. Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1417.jpg

Next I put a thin film of GMS, (GM sealer that you can get at any GM dealer) inside the rim of the band. This will ensure it stays water tight and will also keep the band in place. This stuff turns to the consistency of pure rubber when it dry. Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1422.jpg

Now just slip the band on and put a large adjustable clamp around it to hold it in place over night. As you can see, I used tape around the edge since the cover has new paint on it. The sealer will squeeze out a little around the edges. That's what you want so you know it's sealed well. When it's dry the tape line makes it easier to clean off the excess. Resized to 45% (was 1023 x 685) - Click image to enlarge DSC_1426.jpg

Well, that's about it. Let it cure well, clean it up, and it's ready to install the next day with the desired odometer setting.

Hope this helps with your next project.



Thanks to forum member LRCXed for the fine photos and write up on the topic of resetting mileage and needle removal.

Here's a method to test how accurate your speedometer is.

A simple way of testing the accuracy of a speedometer may be just to time how long it takes the odometer to show exactly 1 mile. Take that number in seconds and divide it into 3600. That will give you the MPH that the needle should show. i.e. Let's say it takes 108 seconds for the odometer to turn 1 mile. Divide 3600 by 108 and the MPH that the dial should have shown would be 33.33 MPH.

Bluefox adds. I also test my speedometers at 2 miles, 3 miles and 5 miles.

by Blue Fox

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