1972 CB350K4 Tachometer
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Thread: 1972 CB350K4 Tachometer

  1. #1
    Senior Member barab63's Avatar
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    1972 CB350K4 Tachometer

    With the engine running, the tachometer needle does not lift off the peg easily, but will after goosing the throttle a bit. Then it will indicate the idle speed and above. In the attached pics, I've marked where I think lubrication might be needed. Question is where and what type of lubrication? A light machine oil (the type used to lubricated electric clippers? 3 in 1? Something special? Thanks.

    1972 CB350K4 Tachometer-inked101419-cb350k4-tach-1_li.jpg

    1972 CB350K4 Tachometer-inked101419-cb350k4-tach-2_li.jpg

    1972 CB350K4 Tachometer-inked101419-cb350k4-tach-3_li.jpg
    Current projects: 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500

  2. #2
    Senior Member barab63's Avatar
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    Anyone have experience with this?
    Current projects: 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500

  3. #3
    Super Moderator longdistancerider's Avatar
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    There's no lubrication used in the tach or speedo other than at the drive section where the cable attaches, that's light oil used there. I think your problem is that the viscous fluid in the needle drive section is low or congealed. I have no idea about how that gets cured.
    Maybe contact these people? https://www.cb750faces.com/cb750face...ation-services
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


    https://www.hondatwins.net/forums/22...d-attempt.html and https://www.hondatwins.net/forums/1-...r-attempt.html
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  5. #4
    Junior Member drbsmith's Avatar
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    I just repaired the same issue on my CB450. The original lubricant gelled up and ended up in the bottom drum causing a clearance(dragging) issue between the lower drum and the magnetic disk. On my CB450, they are at an angle to each other which allowed me to get in with a cotton swab and rubbing alcohol to clean it. However, after I looked closer, I decided to take it apart more and was able to clean it out better. I also followed the detailed instruction in the link below on very lightly re-lubricating the proper spots on the tach. It works perfectly again.
    https://xjbikes.com/forums/threads/s...th-pics.15303/

  6. #5
    Senior Member barab63's Avatar
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    This info should prove very helpful. Thanks to longdistancerider and drbsmith.
    Current projects: 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500

  7. #6
    Senior Member barab63's Avatar
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    1972 CB350K4 Tachometer (recrimping the ring)

    Okay. Decided not to mess with the operation of the unit; it functions well enough, and I don't want to disassemble it any further. Cleaned the lens both sides, and used a little canned air. Now I need to re-clamp the ring around the outside. I had pried the ring up on the bottom side very carefully to get it apart.

    1972 CB350K4 Tachometer-101419-cb350k4-tach-ring-1.jpg

    1972 CB350K4 Tachometer-101419-cb350k4-tach-ring-2.jpg

    1972 CB350K4 Tachometer-101419-cb350k4-tach-ring-3.jpg

    1972 CB350K4 Tachometer-101419-cb350k4-tach-ring-4.jpg

    I need to re-crimp the ring, with no or minimal marks on the top side of the ring. I thought to make a jig to hold the unit face down in place, and use a piece of PVC with the same ID and the OD of the unit to force the uplifted side of ring back to flat (clamping the upper and lower portions together. Not sure if pressing the PVC down uniformly will yield the best result. Any other ideas are encouraged and welcome. Thanks
    Last edited by barab63; 10-27-2019 at 07:36 PM.
    Current projects: 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500

  8. #7
    Super Moderator longdistancerider's Avatar
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    I'm going to be in the same position of clamping that ring down soon. Waiting on new rings since mine are pretty bad.
    I'm thinking the PVC pipe to set the gauge into and then peen the ring over with a small tap hammer. Other thought is a pair of duck bill pliers w/o teeth, pretty hard to find, with a piece of rubber/leather to protect the face finish of the ring.
    Definitely need some sort of cushion between the gauge and PVC to protect the housing finish.
    Looking at some of the photos from different people who rebuild these for a living shows a board with a cutout for the housing to fit in protected with cloth.
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


    https://www.hondatwins.net/forums/22...d-attempt.html and https://www.hondatwins.net/forums/1-...r-attempt.html
    Road Trip https://www.hondatwins.net/forums/11...here-i-go.html or "where's Jim now?"
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  9. #8
    Super Moderator ancientdad's Avatar
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    I think the hardest part of the reassembly is the pressure you have to keep on both halves to keep the soft rubber ring between the halves compressed so the metal ring will lap over the bottom half while you crimp. Mine were so hard to keep together and crimp at the same time that I ended up with permanent trigger finger on my ring finger of my right hand from continuous gripping of the duckbill pliers, probably because I hadn't used that much grip continuously for a couple decades since getting into a softer line of work. My duckbills had worn teeth and though they left some marks on the upper side of the ring, I helped disguise it by taping off the side of the ring when I re-painted the upper half satin black, allowing the satin paint to cover the horizontal upper surface of the ring, and it blends in with the upper cover and isn't as noticeable
    Tom

    CL450 project reboot, street legal this time
    Budget drag bike project
    CB350K1 full patina project
    Ride along at the drag strip


    running points... because I'm too old for mysteries that begin with pushing

  10. #9
    Member pidjones's Avatar
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    On GL1000 and CB750F units I've done, I used some cheap racheting bar clamps from Harbor Freight to press it all together and just used regular pliers to re-crimp. Came out looking fine. On all of these, my problem was non-response or very slow response and return of the needle. A partial drop of silicone lubricant gathered on a toothpick from the spray can lid placed carefully on the needle bearing thined out the old, thickened lube and returned normal operation. I didn't mess with the odometers.
    longdistancerider likes this.

  11. #10
    Senior Member barab63's Avatar
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    1972 CB350K4 tachometer Recrimped

    I decided to make a jig and a crimping tool. Jig, tool, and results are below. Can of grease not included in the process.

    Jig: compresses the two halves together
    1972 CB350K4 Tachometer-cb350-tach-crimp-jig-1.jpg
    1972 CB350K4 Tachometer-cb350-tach-crimp-jig-2.jpg


    Tool: Untapped plier jaw works on the bottom of the ring. Top of ring shows almost no marks from this process.
    1972 CB350K4 Tachometer-cb350-tach-crimping-tul.jpg


    Clamp ring reinstalled: worked a cross pattern (N/S/E/W) going very slowly around the ring, one plier jaw width increments.

    1972 CB350K4 Tachometer-cb350-tach-rng-recrimped-1.jpg

    1972 CB350K4 Tachometer-cb350-tach-rng-recrimped-2.jpg

    1972 CB350K4 Tachometer-cb350-tach-rng-recrimped-3.jpg

    1972 CB350K4 Tachometer-cb350-tach-rng-recrimped-4.jpg


    Up until now, I have not included many pictures of the progress made on this bike. Combination of forgetful and lazy. Hope to improve. And I hope this post proves helpful to someone else. Thanks for the feedback.
    Last edited by barab63; 10-28-2019 at 06:37 PM.
    Current projects: 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500

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