Note: These steps and directions are purely suggestive. If you feel that there is a better way to disasemble your gauges please do so. We take no responsibility for damaged parts. As an additional note, take your time and be very careful. In most cases these 30+ year old parts are sensitive and brittle.
These instructions are specific to a 1972 CB350 K4 Speedometer, but much of the information will apply to other gauges.
The first step is to remove the metal band that holds the case and backing plates together.
Start with a large hose clamp and a piece of rubber. You can find a similar piece of rubber at any hardware store as a "discharge" hose. Cut it to size and this will protect the metal band on the gauge from the hose clamp.
The hose clamp will preserve the round shape of the band when you are prying the metal lip up. Locate the bottom of the gauge and place the screw part of the clamp on the bottom, as this is the least visible part of the gauge. Tighten down the clamp so it is snug, but not too tight because then the clamp will dent the outside of the metal band. I found that a paint can opener works well for starting to lift up the band on the back side. You will need to file the end of the opener down to a sharper lip so you are able to get the opener under the band. This is the most difficult part about pulling these vintage Honda gauges apart. Be patient and use caution. The 1-piece metal ring seals the gauge together. You will need to take your time as it will take many passes to get the ring started and lifted up.
After your many passes around the metal band you should be able to get a set of small flat pliers on the metal band. I wrap a piece of duct tape around the one end of the pliers to protect the outside of the metal band from any markings. Now you can start bending the band so it's parallel to the case. Having the metal band fully open will make for easier disassembly and re-assembly.
Next step is to remove the trip meter knob. There is a small screw in the end of the knob. Remove this screw, and the knob can be pulled off. A heat gun may help with the loc-tite that is holding the screw. Be careful not to strip the head.
If you are painting the cases (Satin black) Leave the rubber housing attached to the case. It will be much easier to remove once the entire backing plate and the guts are removed from the case. Removing the knob only (not the rubber housing) will allow you to remove the entire backing plate and guts while the rubber housing stays in place. Once the band if fully open and the trip meter knob is removed, you should almost be able to pull apart the two piece by hand.
If you cannot, go back and open the band up some more. If needed, you can very carefully insert a flat blade screwdriver between the housing and the backing plate. Be careful though because underneath is a rubber seal that you do not want to damage. If you are painting the case, go ahead and remove the rubber housing for the trip meter now. It's easier to remove once the guts have been removed. These can be brittle, so use caution when removing. A heat gun may help soften the rubber. Now that the case and backing plates are separated, it's time to remove the needle and the face plate mounting screws. The needle is a pressed fit, but many times it's a very tight fit. I used a pair of small, curved, needle nose pliers.
DO NOT LEVER THE NEEDLE OFF. THIS WILL BEND THE THIN FACE PLATE AS WELL AS BEND THE NEEDLE BEHIND. Make sure you are prying up behind the round chrome center as the actual needle is thin metal and could bend. A head gun will help loosen any glue used to secure the needle. Use caution as there is a possibility of melting the plastic numbers behind and melting other components. Pull directly upward to remove the needle. Again, do not pry or lever the needle off. Now remove the two face plate mounting screws.
Now the plate can be removed.
Now it's time to strip and prep the face plate. Make sure the face is very clean. It is a good idea to sand the face with a 600-800 grit paper then wash clean. Wipe the surface and your fingers with denatured alcohol before handling and applying the new face laminate. Now it's time to adhere the new face onto the clean plate.
It is easier to place the new face onto the plate by completely removing the protective paper on the face. Use caution when removing the protective paper. Hold the new face down with your finger and carefully roll the protective paper off the face. If not done carefully and slowly you could stretch or tear the new face. Leave the new face on the protective paper on the back until you are ready to place it onto the plate. Use some fresh clean water and lightly mist the plate with the water. Do not drench it in water. This will allow some movement for final placement of the new face. Carefully align the screw and needle cut-outs with the plate. Using your clean finger, start in the middle and LIGHTLY start to apply the new face to the plate. Start in the middle and work your way to the outer edge. This will remove any air pockets as well as push the water out.
Once it's in place, where you want it, take a lint free, smooth cloth (to avoid scratching the new face) and firmly apply the new face to the plate. Be sure to get the edges of the odometer and trip meter holes firmly placed down, as there is a slight dip in the plate from the metal punching process. Allow the new face and plate to dry at room temperature for at least 24 hours. Do not leave it out in a cold garage, because the adhesive will not cure properly. DO NOT take a heat gun or blow dryer to it to hurry up the process. After the new face and plate have been cured for 24 hours, use a razor to trim the trip and odometer cut-outs, and any edge overhang that may occur. You can now re-install the face plate to the guts and backing plate, two mounting screws, and needle.
We suggest touching up the needle tip with a dab of model paint that matches the red-line. The needle is a simple press-on fit however; make sure the mounting needle is at its resting spot at 0 mph. If you removed the rubber housing for the trip meter and painted the cases, now is the time to re-install the housing, before the guts go back inside the case. Insert the whole backing plate back into the case. Check your work before crimping down the metal band. Make sure the glass is clean, and there is no other debris inside, etc. Make sure the trip knob turns correctly. With all that checked, now it's time to crimp down the metal band.
This also needs to be done with caution especially if you painted the outer case. Using the same flat pliers with duct tape wrapped around one end, carefully ROLL the upper edge of the metal band towards the center. DO NOT SIMPLY SQUEEZE THE PLIERS TOGETHER. THE BAND NEEDS TO ROLL ONTO THE BACKING PLATE FOR A TIGHT FIT. Make sure the band is tight up against the case before rolling the upper part. This is also a tedious task and needs some patience. Once the band is rolled over, you can actually start to crimp the band down as tight as possible.
Be careful not to mar up the outer edges or the front side of the band or the case. The band will not be seen on the back side, but do your best to get it as flat as possible.