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  1. #1

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    Default 1978 Shovelhead top end noise

    Hey everyone. Recently picked up a 78 flh. So hereís the thing, the bike makes a pretty shaky rumble type noise when running. been doing a lot of research as to what it could be and Iíve found that it may be rocker endplay or also piston slap. Does anyone have any ideas? Thanks a ton. Hereís a video of the noise.

    https://youtube.com/shorts/sqBEuIRMpDw?feature=share

  2. #2

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    Also, I’ve already adjusted pushrods and all are good.

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    Use a stethoscope or even a long screwdriver to pin point where the noise is coming from. That will tell you a lot.

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    Quote Originally Posted by ncmc47 View Post
    Use a stethoscope or even a long screwdriver to pin point where the noise is coming from. That will tell you a lot.
    I’ve done this and can’t quite seem to tell what I’m actually looking for, this is my first BT. I guess what I should ask is if any of you guys have any guesses as to what it could be before I take it apart? Going to start with rocker shafts and work my way down, but it would help to have some more insight. Thanks again!

  5. #5

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    Rocker arm end play spec is something like .004 - .025, so don't bother with that. You won't hear the rocker arms anyway.

    If you suspect that the valve train is the source of the noise, remove the tappet blocks and check the tappet rollers and cam lobes carefully.

    A steady knock at idle that goes away as rpms increase is often due to a worn compensating sprocket, or a loose motor pulley if the primary is a belt drive.

    A galled piston will usually make a noise that is more of a "tink" than a "clunk".

    Jim

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    tink n clunk would be a good name for a bar,,,,,,,,

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    I'll drink to that ...

    Since this scoot is a unknown to you ...

    Why not tear it all the way down, get to know it type deal ...
    Ya might see the needs for some upgrades along the journey ...

    ... /// https://youtu.be/QDYwLhgHl64 \\\ ...
    Last edited by Dragstews; 08-20-2021 at 1:42 PM.

  8. #8

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    Quote Originally Posted by Hubbard View Post
    tink n clunk would be a good name for a bar,,,,,,,,
    Hey we have the same last name! And I agree drag, just thought I’d check with the cc wizards. Going to hustle it over to born free next weekend then it’ll be tear down time after that. I’ll post pics for anyone willing to lend a helping hand.

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    Quote Originally Posted by JBinNC View Post

    A steady knock at idle that goes away as rpms increase is often due to a worn compensating sprocket,

    Jim
    This!

  10. #10

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    Read about the compensating sprocket earlier. I’ll check this as well. Anyone know a good way to test the play? Also I checked the tappet screen and there wasn’t a screen or spring inside… am I fucked?

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    nope, buy a screen and spring. open the primary, check the chain tension, it's tensioner and see if the compensator has play in it.
    Last edited by Fetch; 08-21-2021 at 6:12 PM.

  12. #12

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    Quote Originally Posted by Fetch View Post
    nope, buy a screen and spring. open the primary, check the chain tension, it's tensioner and see if the compensator has play it.
    And primary chains in aluminum cases must be adjusted correctly, and that will be much looser than you think. 5/8 - 7/8 slack, cold, at the tightest spot in the run. You must rotate and check at the tightest spot you find. Chains adjusted tighter will be banjo string tight when hot (operating temperature) and that causes all manner of problems.

    The compensator should have some give when the chain is rocked back and forth (that's its function). The cover should be tight, and if you can rotate the cover by hand, that indicates wear at one or more places in the assembly. Many people have good luck with just replacing the compensator with a solid sprocket. That is a cheap fix nowadays, as factory compensator parts are hard to come by, and a lot of the import stuff is junk.

    Jim

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    Quote Originally Posted by hubsripz View Post
    Read about the compensating sprocket earlier. I’ll check this as well. Anyone know a good way to test the play? Also I checked the tappet screen and there wasn’t a screen or spring inside… am I fucked?
    If you have hydraulic tappets, unscreened oil ain't doing them any good, and that might be the source of your noise.(bad hydraulic unit from swarf in the oil). If you have a solid tappet conversion, the screen isn't absolutely necessary (but doesn't hurt to screen top end oil anyway).

    Jim

  14. #14

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    Click image for larger version. 

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    So I took the primary cover off and found that this drum looking thing behind the nut was loose. Is this supposed to be loose and movable by hand or tight?

  15. #15

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    That's the cover, it has a stack of belleville washers in it that provide the spring pressure. If the cover can be turned easily by hand, the assembly has enough wear that it might make noise. Just for simplicity's sake, you might want to do the solid sprocket conversion, it's not expensive.

    Jim

  16. #16

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    Quote Originally Posted by JBinNC View Post
    That's the cover, it has a stack of belleville washers in it that provide the spring pressure. If the cover can be turned easily by hand, the assembly has enough wear that it might make noise. Just for simplicity's sake, you might want to do the solid sprocket conversion, it's not expensive.

    Jim
    Is there anyway to temporarily shim this? I’m going to be upgrading to on open belt primary soon, just trying to make it down to born free.

  17. #17

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    Yes. Add a belleville washer from another cover, or add a large washer inside the assembly. I used to do that with a Torrington thrust washer that I found that fit perfectly and was hardened. Do not add a washer under the head of the nut on the outside of the cover. That will pinch the cover and keep it from turning, but will not address the wear problem or stop the noise.

    Keep in mind that the compensator may not be the source of your noise, although it's a good bet.

    Remove the nut and cover and you will see how that assembly goes together. You will need a jam bar to go between the two sprockets and a BIG pull bar. Tighten with a torque wrench to 150 - 165 ft.lb.

    Jim

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