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Early model 70-71 instrument rebuild/rejuvenation

Discussion in 'The Garage' started by TwoManyXS1Bs, Oct 15, 2013.

  1. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    This thread and series of posts covers the return-to-acceptable or return-to-functional service work done on an XS1B tachometer that had a severely sunbleached dial face, was exhibiting jittery/jumping needle and had poor internal illumination.

    The terms 'overhaul', 'restoration', 'renew', 'refurbish', 'remanufactured', 'rebuild', generally mean a higher level of repair work, and are not really achievable here. An old instrument can have external damage and blemishes, internal cosmetic fading and blemishes, and internal mechanical wear/damage and problems. We can try to resurface blemished outer shells, polish up bezels, touch-up dial faces and needles, but at this time the only option is to acquire used instruments, clean and fix movement damage, including needle shaft bearings, and try to build a better instrument from the parts.

    Here is a used tachometer that has a less-than-stellar enclosure, missing turn signal indicator lens, internal mechanical problems, but a useable dial face and pointer.
    TachA01.jpg

    Update: Thread edited 11/22/2016, fixing pic display and ordering in the posts.
     
    Last edited: Nov 22, 2016
  2. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    The `70-`71 XS1 and XS1B instruments have a totally plastic enclosure, bezel and bezel ring. As such, they cannot be opened up like later models, which use crimp rings on metal shells. Instead, we must carefully cut through the plastic shell at a location that minimizes cosmetic damage.

    Use a jewellers saw with a thin/coarse blade. The blade will load up with plastic and must be brushed clean frequently. Saw along the joint between the upper and lower shells, using the broad shelf-like edge of the upper shell as a guide. The thickness of the plastic to be cut is about 4-5mm, and this will take quite some time. Avoid allowing the sawblade to penetrate more than about 6-8mm, to prevent damage to the internals.
    TachA02.jpg
     
    Last edited: Nov 22, 2016
  3. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    After sawing completely through, separate the two shells. This pic shows an instrument with acceptable enclosure and indicator lenses, but a sun-bleached dial face and jittery movement. The black part of the upper shell cut edge shows just how thick the plastic is to be sawed.
    TachA03.jpg
     
    Last edited: Nov 22, 2016
  4. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    The next step is to remove the pointer, without damaging the dial face. Apply low-adhesion painter's masking tape alongside the pointer shaft.
    TachA04.jpg
     
    Last edited: Nov 22, 2016
  5. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    The pointer is press-fitted on a gently tapered shaft, and considerable force must sometimes be used to remove it. Some folks use leveraging tools and screwdrivers, I prefer to use my fingertips only, which gives a better guaranty of minimal damage, wedging them under the pointer body, and using a wedging/squeezing motion only, pop-off the pointer.
    TachA05.jpg TachA06.jpg
     
    Last edited: Nov 22, 2016
  6. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Using a finely-fitted screwdriver, carefully but firmly remove the dial face screws.
    TachA07.jpg

    The registration/fit of the dial face and screws is somewhat sloppy, make note of the screwhead indentation on the dial face, if possible.

    Then gently lift the thin aluminum dial face from the instrument.
    TachA08.jpg

    Later instruments use a thicker plastic dial face, only these early models use the delicate thin aluminum.

    Notice the metal hood of the nighttime illumination bulb hole, above the movement. The hood needs to face inward, toward the inside, to provide even illumination around the outer ring of the instrument interior. The hood is a tubular slip-fit over the illumination bulb hole, held by a small dab of glue, long dried and cracked.
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  7. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Backside view of instrument lower shell, and illumination hood.
    TachA09.jpg

    Remove the two 5mm movement screws.
    Remove the movement assembly.
    TachA10.jpg

    Notice the thickness of the saw cuts, and where the sawblade might accidently cut into one of the indicator lamp tubes.
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  8. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Remove the two metal indicator light tubes, being careful to avoid damaging the potentially brittle rubber tube-gaskets.
    TachA11.jpg
     
    Last edited: Nov 22, 2016
  9. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Two instruments at the first level of disassembly.
    TachA12.jpg

    Close inspection and selection of the best parts can be done here.

    Next chapter: Movement inspection and disassembly
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  10. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Chapter 2 - Movement inspection and disassembly

    For this type of work, I like to use magnified optics, like this headband type Optivisor with a #5 lens.
    This Optivisor is older than the instrument, a fitting tribute to this oldschool stuff.
    (Picture accidentally taken by author, puzzled over smartphone camera icons)
    TachB00.jpg
    Speedometer and tachometer instruments typically use a round pot-magnet, shaft mounted and driven by a flex cable with a squared end that fits inside the instrument main shaft. This round magnet fits closely inside a separately-mounted aluminum cup or ring, which is fitted to the pointer shaft.
    The spinning magnet induces eddy currents in the surrounding aluminum ring, which creates small magnetic fields within the aluminum, and this imparts a torque on the aluminum ring, which tries to rotate in the same direction as the spinning magnet. Similar principle as used on older utility spinning-wheel type power meters.

    These delicate instruments are trying to function in a harsh motorcycle environment. Subjected to vibration, sunlight, rain, the occasional "Hey y'all, watch this!", heat and cold, it's a wonder they work at all. Materials within the instrument age, rot, decompose, and ends up fouling close clearances. Lubrication dries up and bearings rattle/wear. When the aluminum ring starts to rub/catch on the spinning magnet, it flings about and tries to self-destruct as it slams into the stops.

    Commonly found problems in these types of movements are:
    - Loose screws and pointer/needle
    - Dirt/debris in the close-fitting interface of magnet and cup, causing drag and 'catching' of the aluminum ring
    - Dirt/debris in the spiral-wound return spring
    - Worn mainshaft, allowing magnet to deflect and physically contact/drag on aluminum ring
    - Worn or bent pointer shaft
    - Worn pointer shaft end/thrust bearing, allowing the aluminum ring to contact the spinning magnet
    - Dried, minimal, or missing damping grease in damper unit
    - And, the newest malady, if the instrument has been opened up before, previous owner creativity

    Take the movement unit, look for damage, debris, looseness of parts. Fit a small screwdriver or piece of drive cable into the mainshaft drive end, rotate and wiggle, looking for excessive wobble of the spinning magnet. Grasp the pointer shaft, move it in-out and side-side, looking for sloppy fit You can temporarily fit the pointer (lightly) on the shaft, if that helps. Rotate it, checking for a dry damper cup and spiral-wound return spring binding.

    In the second attached pic, you can see how a dragging/catching aluminum ring has been banging against the stops. This is not a terminal condition, as repairing the pointer shaft end bushing stopped the dragging/catching, and the aluminum ring functioned fine. Notice that the spiral return spring is not deformed, and each wind is concentric, not touching each other and binding.
    TachB01.jpg
    If the movement is clean, presents little or no sloppyness, no dragging of the magnet and ring, pointer shaft rotates fully without binding, slowly returns to 'park' position, and seems to function properly, it may not need disassembly, and could be simply cleaned and lubricated (see later in this thread) and returned to service.

    Otherwise, the next step is a thorough cleaning, using a suitable cleaning aerosol, like brake cleaner, electronics cleaner, firearms cleaner, or the difficult to find instrument cleaner. Spray aggressively, except on the delicate spiral spring. Spray this spring gently, removing debris from the coil winds. Check again for looseness, sloppyness, and dragging.
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  11. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    You will need a properly fitted wrench to loosen the front pointer shaft bushing lock nut. The size used here is 13/64" (5 mm). The front bushing is also the damping unit. A thick viscosity grease inside the damping cup provides just the right amount of 'cling' to the pointer shaft, removing erratic vibration-induced pointer bouncing. The exposed front end of the bushing has screwdriver slots, so you can adjust end play. At this time, while the movement assembly is still together and can tolerate the torque forces, you only want to loosen the lock nut.
    TachB02.jpg

    If the movement is in good shape:

    You may only need to adjust the end play to achieve good pointer movement. If so, apply a tiny dot of heavy lubricant to the rear thrust bushing and adjust end-play to about .005" - .010" (0.10 - 0.25mm).

    If the damper cup is dry or not properly damping the pointer motion, it can be refilled. The preferred damper fluid is a thick viscosity silicone-based instrument damper grease. The preferred method is to press an injector tube directly onto the damper locknut, over the pointer shaft, and inject this fluid, through the bushing, into the damper cup, watching for overflow. Similar to greasing automotive ball joints. Then thoroughly clean off all exposed fluid.

    A note on damping fluid: Back in the day, motorcycle shops received bulletins about proper instrument storage. If the instrument is stored upside-down, bezel down, the damping fluid would, over time, slowly ooze out of the damper cup and onto the backside of the instrument bezel, ruining the appearance, and reducing the damping feature. Many instruments were tossed because of this. Store yours accordingly...
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  12. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    On the left of the movement frame (as viewed from front) is the adjustable stop finger. This establishes 'zero' for the instrument, and you should mark its current position prior to removal. Outline it with a fine tip felt pen. The arrow here tell me that this stop sits fully to the indicated side.
    TachB03.jpg TachB04.jpg
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  13. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Next is removal of the 'zero' stop arm. Properly fitting screwdrivers are a must, these screws were installed with lock washers, and, over the years, have taken quite a 'set'.
    TachB05.jpg

    Had to use toothed needle-nose pliers on this one. FIRMLY grip the head of the screw before attempting to turn. It'll 'snap', then turn easily.
    TachB06.jpg

    Remove the stop arm, some bit of articulating/rotating is necessary to withdraw it.
    TachB07.jpg

    Next chapter 2-b: Disassembly of movement framework
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  14. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Chapter 2-b: Disassembly of movement framework

    For the rest of this procedure, you may want to back off on the alcohol and pharmaceuticals for a coupla days. We will be conducting brute force in a brain surgeon manner on a delicate instrument. The staked retention notches must be chiseled back to allow removal of the front plate, and in a way that retains enough metal to allow peening the notches during reassembly. The frame must be solidly clamped in a sturdy vice, that allows access to the staked notches, but doesn't harm the delicate aluminum ring and spinning magnet.

    The first pic shows a old/broken punch that has been reground to chisel under the staked notch, and shove the metal slightly back, just enough to allow the front plate to clear.
    TachC01.jpg

    This first pic was a 'staged' shot, and doesn't show the original stake job.

    The second pic shows the appearance of a factory/original stake job.
    TachB02.jpg

    The third pic shows what the chisled-back staked metal should look like.
    TachC02.jpg

    You should be able to barely see the notch opening of the front plate, revealed during the chisling operation. Notice that the front plate is slightly recessed into the side plates.
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  15. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    The first step to removing the freed front plate is to gently tap it out of the retention notch, as shown in this first pic. Braced atop a solid piece of steel, a gentle tap will pop it out. But, stop before it flies out. Do both sides like this first.
    TachC03.jpg

    The second pic shows the result, the front plate is released, but still confined by the side plates, preventing damage from an uncontrolled ham-handed disassembly.
    TachC04.jpg
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  16. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Now place the movement frame on a clean/padded work surface, and, using a fine/flat screwdriver, gently pry the front plate free of one notch, then the other.
    TachC05.jpg

    Now you can carefully withdraw the front plate (which carries the aluminum ring, damper and pointer shaft as a sub-assembly).
    TachC07.jpg TachC08.jpg

    The remaining u-shaped rear frame and side plates carry the rotating magnet and mainshaft as the other sub-assembly.
    TachC09.jpg
     
    Last edited: Nov 22, 2016
  17. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Closely examine the two sub-assemblies for damage, loose fits, dirt/grease/grime and particles stuck within the rotating magnet shroud. Thoroughly clean again, especially trying to flush-out the rotating magnet mainshaft and rear housing bushing.
    TachC10.jpg

    The rotating magnet main shaft does not necessarily need to be a perfect/pristine fit into the rear housing, a little looseness is fine, and will allow lubricant to flow into the shaft bearing area. My favorite is chain lube, or any aerosol 'liquid grease'. The lubricant will flow freely into the bearing shaft area, then the lubricant's carrier/solvent will evaporate out, leaving a thicker grease that lasts for years.

    If the main shaft fit is okay, you may lubricate it now, ensuring complete lubricant penetration. I will usually hold the rear housing vertical, magnet side down, apply lubricant to the upper part of the shaft, alongside where the square drive cable enters, coupla drops, then rotate/slide the shaft to get lubricant to wick into there. Continue adding and working lubricant in there until it starts to emerge from the bottom of the housing bushing, just behind the rotating magnet. You can lubricate it later, just remember to do it.

    If the main shaft fit is too wobbly, it will need to be disassembled further. The rear housing will need to be drilled-out for a fabricated bushing.
    TachC11.jpg

    Next chapter 3: Inspection and disassembly of pointer/needle movement.
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  18. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Chapter 3: Inspection, disassembly and servicing of the pointer/needle movement

    We are now at the delicate heart of the instrument. Extreme care must be exercised when working on this movement. Any action that stresses the spiral-wound spring beyond its 'yield' zone will require meticulous adjustments to return it to normal.

    This pic shows the most likely cause of instrument malfunctions, the rear support bushing. The very tiny pointer shaft fits into a very tiny hole in this bushing. Being such a small bearing size, it doesn't hold much lubricant. Vibration forces distributed over such a small area create very high localized loads, accelerating wear. As the wear starts to wallow-out the bearing hole, the shaft bounces about, increasing the wear even more.
    TachD01.jpg

    This bushing is little more than a small round brass button, press-fitted and staked into a bearing support arm. Next step is to carefully remove that arm and inspect the bushing.
     
    Last edited: Nov 22, 2016
  19. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    The rear bushing support arm is held with another of those tiny screws that are very tight and have taken a 'set'. The base of the arm has two dimples that fit into corresponding holes in the front plate, providing precise alignment. Nevertheless, marking/outlining with a fine point felt-tip pen is still recommended.
    TachD02.jpg

    The aluminium ring is supported by a single, wide arm. The 'zero' stop sets that arm position, and the arm hits the rear bushing support to arrest travel in the other direction. Note that this arm must be on the upside (clockwise as viewed from front) side of the rear bushing support during reassembly.
    TachD03.jpg

    Tightly grasp the head of the screw with toothed needlenose pliers, then 'snap' it loose. Remove with a well-fitted screwdriver.

    The support arm can now be carefully removed. It must be rotated and articulated carefully, and in such a way that it ends up reversed/upside-down to allow withdrawal.
    TachD04.jpg
     
    Last edited: Nov 22, 2016
    gggGary likes this.
  20. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    The damper cup can now be serviced. If damping is not a problem, and damping fluid remains in the cup, it can be left as-is.
    TachD05.jpg

    If the damper cup is dry or not properly damping the pointer motion, it must be cleaned and refilled.

    Gently withdraw the aluminium ring and pointer shaft rearward about 1/4", revealing the brass inner adjuster/bushing, Carefully/gently clean in there, using aerosol cleaners and toothpics, removing old/dried damper fluid. Note that the spiral spring will tolerate up to 1/2" of rearward displacement without getting bent out of shape. If necessary, the brass inner adjuster/bushing may be removed by unscrewing forward, make note of the original seating depth before withdrawal, then clean thoroughly.
    TachD06.jpg

    The damper cup can now be filled with damper fluid.

    A thick viscosity grease inside the damping cup provides just the right amount of 'cling' to the pointer shaft, removing erratic vibration-induced pointer bouncing, but allows the pointer to return to 'zero', and lubricates the adjuster/bushing. The preferred damper fluid is a thick viscosity silicone-based instrument damper grease. I've had good results using "Lubriplate", a white lithium-based grease, supplied in a tube. This grease has just the right amount of 'cling', and has the consistency of chicken-fried-steak cream gravy, without the flavor.

    If the adjuster/bushing has been withdrawn, you can slide an injector tube directly over the pointer shaft, down into the cup, and inject this fluid into the damper cup. Fill about halfway, accounting for the space used by the adjuster/bushing. Reinstall the adjuster bushing and watch for overflow.

    If the adjuster/bushing remains in place, daub a little grease onto its exposed shaft, and work it in (pic #2).

    Fit the pointer-shaft/damper-cup back over the adjuster bushing, then thoroughly clean off all exposed fluid.
     
    Last edited: Nov 22, 2016
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