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  1. #1
    CB750 Member Andy888's Avatar
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    Primary chain tensioner issue

    Well I have the engine now fully stripped and am in the measuring and check phase. All going fairly well until measuring the primary chain length. The recommended measuring procedure in the manual shows that the measurement is about 10mm too long so a new chain is required. The bottom oil fed tensioner is badly worn on one side and is almost down to the metal. I assume is so worn as the chain is stretched. So onto David silver to but a new chain and tensioner only to find the tensioner is no longer available.
    A used one is more than likely also worn so what have others done? Is there a company that can reline them??




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  2. #2
    CB750 Addict dan1951's Avatar
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    Not to familiar with the F model but they are available on E-bay O.E.M. part number 14500-425-020 fairly expensive at $189.95

  3. #3
    CB750 Member Andy888's Avatar
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    Thanks for the reply but those are the timing chain tensioner. I need the tensioner underneath the primary chain (from crank to primary shaft)


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  4. #4
    CB750 Addict dan1951's Avatar
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    Sorry for the screwup, I see pads (used) but have two retaining screws holding it place.

  5. #5
    CB750 Member Andy888's Avatar
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    Yes. They are the ones on top of the chain. My one seems ok. It's just the pesky one that I can't get. Arghhhh!!!


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  6. #6
    CB750 Addict Chris in Dorset England's Avatar
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    Hi,
    Just an idea, take it to a 3D printer shop, they may be able to replicate the worn part, how you get the worn one off and the new one to stay on will be something else!

  7. #7
    CB750 Member Andy888's Avatar
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    I did wonder about that. I'm not sure what it's made of but we use a structural panel bond at work that's stronger than the metal it's stuck to. But I'm not sure how it would perform in hot oil?? Risky......


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  8. #8
    CB750 Addict Chris in Dorset England's Avatar
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    It looks and feels like a type of hard nylon, I would think there is a glue that would make a good bond, the oil runs at about 80-90c max. There are glues that will withstand that heat.

  9. #9
    CB750 Guru amc49's Avatar
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    In one with no oil cooler the oil temp can easily hit 112 C, at least in the hotter climates. You really want at least 100C anyway as it keeps the water boiled out of the oil. I myself tried to hit 220 F., I have no idea how hot that is in C.

    Don't assume just any plastic can be used there either, the running specs of it are quite hard to get together in one plastic.

    You're looking at one of the parts that no longer being available will stop people rebuilding them..........

  10. #10
    CB750 Addict Chris in Dorset England's Avatar
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    Did you ever resolve the problem with the primary chain tensioner?
    I did ask David Silver if they had any plans to remanufacture these parts?
    "No" was the short blunt answer. There must be a market for these given the 1000s of these engines still around.

  11. #11
    CB750 Member Andy888's Avatar
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    Hi Chris
    Not as such, I bought another used tensioner with less wear on it. Not ideal I know but couldnít find and alternative. Havenít started the engine yet so fingers crossed.


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  12. #12
    CB750 Member Chas's Avatar
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    Need to see if Vince and Hyde will make them in NZ. Their cam chain tensioners are the de facto standard to replace OEM rubbish. Cannot recommend anything else.

  13. #13
    CB750 Addict Chris in Dorset England's Avatar
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    One can always hope! Is there no one in the UK capable of making these things, even in the EU perhaps?

  14. #14
    CB750 Member Chas's Avatar
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    I know Brent Hyde gets his heads made in Italy and I am not sure where he gets the tensioners made, but they could well be local as you need good foundries to make the head and Italy have a lot of these. I will ask.

  15. #15
    CB750 Member Wookie's Avatar
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    Did anyone have luck on sourcing this Primary chain tensioner outside of scavenging from used sources? Mine looks pretty much like your photo.

  16. #16
    CB750 Addict Chris in Dorset England's Avatar
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    I did ask David Silver here in England if they had any plans to remanufacture these tensioners, the short answer was "No". Surprising considering the potential demand.

  17. #17
    Moderator dirtdigger's Avatar
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    The DOHC doesnt have near the following that the sohc motor does. I am sure at some point CycleX will probably offer rebuilt tensioners with their new tensioner material. Doubt many other companies will produce much for parts for these motors.

  18. #18
    CB750 Member Wookie's Avatar
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    So my best bet is to find the best "used" primary tensioner for the DOHC engine? I suppose scouring ebay for used parts sounds like the only option. What is considered a good used tensioner? Mine shows the wear marks in the first post pictures. Can these be safely re-installed or should they be thrown out. Not sure what is considered too far gone. Obviously I would buy new or reman. in a heart beat, but.....

  19. #19
    Moderator dirtdigger's Avatar
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    If it has chunks missing its junk...the material has gotten hard and brittle from the years of being in hot oil and just the general engine heat. Some wear marks are not bad as long as the surface is consistent and not with chunks missing. Your best bet will be to keep watching on ebay for used ones that dont have chunks missing. Maybe go to a dedicated dohc board and ask where they find parts

  20. #20
    CB750 Member Wookie's Avatar
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    Will a 1982 CB900C primary chain tensioner work on a 1982 cb750 super sport?

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