78 GS1000E - Rapping at 2000 RPM

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  • SandPVRR
    #1

    78 GS1000E - Rapping at 2000 RPM

    Hello All,
    Today after a relatively hard down shift (went down two instead of one) I noticed a rapping sound at right around 2,000 RPM. It comes and goes - and if I were a guessing man, I'd say it sounds like the cams trying to switch between the low and high ranges. However, its new, and since I've put less than 1,000 miles on the bike since I've owned it - I'm not sure whats a huge problem and whats a minor issue.
    Is there a lube point up there that I"m missing? Have I just not gotten my cam chain adjusted right? (I haven't touched it) Or are my valves too tight and I'm just noticing it?
    I already found out I have a bad set of points - going to upgrade to electronic ignition - hope I haven't got another issue as well.
    Thanks in advance!
    -Joey
    Tags: None
    • Guest
      #2
      Originally posted by SandPVRR
      Hello All,
      Today after a relatively hard down shift (went down two instead of one) I noticed a rapping sound at right around 2,000 RPM. It comes and goes - and if I were a guessing man, I'd say it sounds like the cams trying to switch between the low and high ranges. However, its new, and since I've put less than 1,000 miles on the bike since I've owned it - I'm not sure whats a huge problem and whats a minor issue.
      Is there a lube point up there that I"m missing? Have I just not gotten my cam chain adjusted right? (I haven't touched it) Or are my valves too tight and I'm just noticing it?
      I already found out I have a bad set of points - going to upgrade to electronic ignition - hope I haven't got another issue as well.
      Thanks in advance!
      -Joey
      You know, you can guess all day, even take a stethoscope and listen to the insides, but if you want the peace of mind you seek, eventually you're going to have to check stuff out such as the valve clearances, and if you're not willing or able to do the work yourself, take it to the shop for a
      "tune-up."
      P.S. No lube points up there, just engine oil pumped up to that area (your oil pressure light isn't on, is it? and it does work?).
      Your cam chain is adjusted automatically by the automatic cam chain tensioner, you're not supposed to mess with it.
      Now a unfamiliar noise is a minor issue compared to a burned valve from too tight a clearance, but too much of a valve clearance and it could get get a little noisy. Is there any way you can find out when the valves
      were adjusted last? How's your oil level looking?

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        • Big T
          Forum LongTimer
          Past Site Supporter
          Super Site Supporter
          • Mar 2005
          • 12392
          • West Slope, OR
          #3
          Originally posted by SandPVRR
          It comes and goes - and if I were a guessing man, I'd say it sounds like the cams trying to switch between the low and high ranges.
          -Joey
          Where do you come up with this stuff? Cams don't switch anything

          Have you gone down the list of all the things you should check/adjust/update in your megawelcome?

          Two I'll suggest

          1. Adjust valves
          2. Service camchain adjuster
          1978 GS 1000 (since new)
          1979 GS 1000 (The Fridge, superbike replica project)
          1978 GS 1000 (parts)
          1981 GS 850 (anyone want a project?)
          1981 GPZ 550 (backroad screamer)
          1970 450 Mk IIID (THUMP!)
          2007 DRz 400S
          1999 ATK 490ES
          1994 DR 350SES

            Comment

            • tkent02
              Forum LongTimer
              Past Site Supporter
              • Jan 2006
              • 35571
              • Near South Park
              #4
              +1 on T's comment. How high did the RPMs go during this "downshift event"?
              http://img.photobucket.com/albums/v5...tatesMap-1.jpg

              Life is too short to ride an L.

                Comment

                • Guest
                  #5
                  Adjust the valves!

                    Comment

                    • 850 Combat
                      Forum Guru
                      Past Site Supporter
                      • Sep 2006
                      • 6018
                      • Spokane, WA, and Hampden, ME
                      #6
                      Is it conceiveable that you sheared a tooth on one of the gears? I have done that on British (Norton) gearboxes a couple times. It makes a knock which seems particularly noticable at steady RPM's.

                      Bear in mind that on a normal motorcycle transmission all the gear sets are meshing all the time, so it does it in every gear, but especially the one with a tooth sheared off.

                      If you over-revved it badly from downshifting, there is a number of things that could have gone wrong. Bending or breaking a valve would make it not run on that cylinder, which generally is quite noticeable.
                      sigpic Too old, too many bikes, too many cars, too many things

                        Comment

                        • SandPVRR
                          #7
                          Morning All,
                          Update - Later, as I was riding home, I had to swing in and make one more stop for work. The bike sat in a parking lot for somewhere between a half an hour and an hour (not quite sure, but it was long enough that the engine was cooling and oil was showing up in the sight glass) It hasn't done that rapping sound since.
                          It does still sound fairly noisy around 2000 RPM, but the sound goes away.
                          Regarding my comment about variable valve timing - I could have sworn I read that in the service manual - however - I'm wondering if I skipped down to the Ignition timing page and didn't realize it at the time. My bad.
                          -Joey

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