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Thread: 1978 R100S, Odd noise from right cylinder head

  1. #1
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    1978 R100S, Odd noise from right cylinder head

    Hello Airhead Gurus,

    I have been out thoroughly enjoying my 78 R100S! And as such I have noticed an odd metallic chirping noise from my right cylinder at around 3k RPM- I have a video on youtube here:

    http://www.youtube.com/watch?v=Ej9J2vkAAqw

    The noise occurs at about 10-11 seconds and again at 19 seconds. Valve clearances at correct. Just rechecked them. Any ideas? Thanks everyone!

    Loren

  2. #2
    Bluenoser
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    It doesn't sound like valve train noise, but more like something else that is vibrating with the engine running. Valve train noise is much louder & more clunk like.

    Have you tried putting the bike in gear, pull in the clutch and see if the noise changes or goes away at the same rpm. Sometimes dry throw out bearings can make a similar type of noise and by using the clutch you can either confirm or rule out that it is clutch related noise.

    If you have a piece of tubing or one of those engine stethoscopes you can move it around the engine to try and figure out where the noise was coming from. With a fairing the noise could be coming from just about anywhere on the right side of the bike and the fairing is reflecting the noise.
    1971 R50/5 SWB with R75/6 drivetrain
    2013 DL650

  3. #3
    Administrator 20774's Avatar
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    It almost could be minor pinging. Or you could have just hit a resonance of the system. Also, what about the up/down movement of the rocker blocks? You should check those at the time of setting the valves. On the side that you're setting the clearances, grab the rocker extension with a thumb and fore finger and move up and down. You should only see a minor movement of oil film where the bottom of the rocker meats the pillow block.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by 20774 View Post
    It almost could be minor pinging. Or you could have just hit a resonance of the system. Also, what about the up/down movement of the rocker blocks? You should check those at the time of setting the valves. On the side that you're setting the clearances, grab the rocker extension with a thumb and fore finger and move up and down. You should only see a minor movement of oil film where the bottom of the rocker meats the pillow block.

    I should've mention that- The up/down play between the rockers and pillows blocks I had checked and adjusted as needed along with valve clearances (as per Snowbum and several other valuable resources. Only minor movement of oil film there- check!

  5. #5
    Registered User PAS's Avatar
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    Have you checked the rocker arm bearings. Some of the early cages cracked on the ends and the needles fell out. Just a thought.

  6. #6
    James.A
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    Right side?,....chirping noise?,.....crank case breather?

  7. #7
    Registered User 6659's Avatar
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    I heard a noise like that once and after much consternation it turned out that the dual metal strap holding on the horn had one side broken. Check that out before tearing into the bike.
    77 R75/7
    78 R100/7
    93 R100R
    95 MZ Tour

  8. #8
    jimmy armour
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    cylinder noise

    try to look inside the plug hole to see if there is carbon build up in the piston valve grouve,s you might see touch marks ,also try to open up the valve clearences to say 10 thou,and see what happens, I had this once while fitting a sports cam, check inside the rocker cover for any touch marks,good luck,Jimmy

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    Administrator 20774's Avatar
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    Stray thought here...could it be the pushrods hitting the inside of the pushrod tubes/gasket where the head joins the cylinder? If the head gasket is put on wrong, part of the gasket will stick out into the pushrod tube, thus allowing the rod to touch it under certain conditions. DAMHIK.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    I will investigate further tomorrow after I find my mechanics stethoscope and report back. Thank you for the points to check!

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    Check your pushrods

    Take a look at them and see if you can get a good look at your camshaft as well.

    How many miles on the bike?

    Do you use any type of additive (Rislone ZDDP) in your motor oil?

    Have you found any extra junk during the last couple of oil changes?

    You could also take a look at your points and plugs while your at it. I have a friend who parked a /2 for 12 years due to a knocking noise in the motor. He finally got around to doing a lower end, top end and a whole lot of hair pulling because the noise was still there after all that. Changed out the bogus repop points and the noise went away, a very time consuming and expensive set of points.

  12. #12
    Registered User toooldtocare's Avatar
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    I bought a used 88 RS in 94 that made a similar noise on the right side. The bike had 12K on it and I put another 12K on before selling it to a friend. The noise bothered him so he had the right side rebuilt (head off, new valves, checked cam and lifters, checked end float, head gaskets, etc.). The noise was still there so he sold the bike back to me after he had ridden it another 6K miles. I put another 12K on or so before selling it again. The noise was still there. I think some engines just make strange sounds at certain resonant frequencies.

    Wayne

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    By Jove, I think I've got it...

    Good news! I am pretty confident I have found the source of my mysterious noise. I found that the bolt that goes through a bracket on the main frame to attach the right horn bracket was "rubbing" on the seam of the fuel tank. For now, I cut a piece off an old bicycle inner tube and wedged it in between. Noise gone! I will try to get a good picture and post it. Gotta see why that bolt is touching the tank and see what I can do to correct it. Cycleman2 you were sure right about the fairing bouncing these noises around and skewing the true source! Thank you everyone for your help- What a load off the mind! I hate even thinking about not being able to ride my Beemer!
    1978 R100S Smoke Red Metallic

  14. #14
    Registered User lmo1131's Avatar
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    Gotta see why that bolt is touching the tank and see what I can do to correct it.
    Do whatever it takes to "re-align" the bracket so nothing rubs on the tank seam; eventually the rubber will wear through and the bolt will be rubbing on the tank again.

    Some time ago my left-side fuel petcock developed a leak - it turned out that the choke cables had worn well-defined "U" shaped grooves through the back side of the petcock and one finally sawed it's way through. I bought new straight-through Karcomas and when I replaced both choke cables I slipped a piece of cloth-covered fuel line over them to act a "cushions". The next time I happened to check (2-3 months) to see if the was any appreciable wear on the back of the new petcock - there was; on both the fuel line piece covering the choke cable and the petcock itself.

    There is no way to prevent the choke cables from contacting the back side of the petcock (using the straight-through petcocks) so there's not much I can do other than replace the them again (this time with later 90? versions (which I don't like the look of)) so I just keep an eye on the situation. Granted this did happen over a long period of time and I was unaware of it, but you might consider a more permanent "fix". A fuel tank would cost a bit more to replace than a petcock.

    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  15. #15
    Monza Blue 1974 R90/6
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    To fix the choke cable eating into the back of the petcock -

    Cut a piece of plain fuel line (without the braid) about two inches long.

    Cut a slit in it lengthwise so you can open it up and slip it over the choke cable where it is rubbing on the petcock. Once you are satisfied with the location and fit, take it off, put some super glue on the inside, stick it back on and you worries about it sawing through the petcock are over.

    Barron

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