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    Shake During Deceleration?

    Hi all,

    I've noticed lately that when I start to decelerate from a cruising speed of 60ish that there seems to be a certain speed that the bike shakes or kinda bounces it seems. It will do this for a few oscillations and then return to normal. It can be seen in the front forks if you look carefully, almost like the neck on the frame is flexing. Or maybe the forks are just bouncing and that's how it looks to me on the bike. I just replaced my rear D404 with a Shinko 230 (front is still a D404 for now) and I can't seem to remember if the bike did this before. Either way the problem has either been aggravated by the new rear tire or swapping the rear tire caused it. I've checked the rear wheel alignment and the chain multiple times and can't find anything wrong. If I roll into the throttle a little bit when the bounce starts it immediatly stops.

    So what gives? Maybe time for new fork springs? The forks are the only thing I haven't rebuilt on this bike except for changing the oil
    The current garage:
    1978 GS750
    1975 GT750M
    1984 CB700SC
    1982 XJ650 Seca Turbo
    1975 RD250 - 350 conversion

    #2
    Steering head bearings need replaced or torqued properly?

    Comment


      #3
      Originally posted by NavyDad View Post
      Steering head bearings need replaced or torqued properly?
      That would be my guess.
      GSRick
      No God, no peace. Know God, know peace.

      Eric Bang RIP 9/5/2018
      Have some bikes ready for us when we meet up.

      Comment


        #4
        I'll have a look at the steering bearings, I did replace them 6 months ago. But to me that doesn't seem like the problem, I can let go of the bars when it does this and I get no headshake. It just sort of bounces, very different than any common problems I've experience before.
        The current garage:
        1978 GS750
        1975 GT750M
        1984 CB700SC
        1982 XJ650 Seca Turbo
        1975 RD250 - 350 conversion

        Comment


          #5
          I would get rid of that Dunlop up front first
          sigpic
          Cowboy Up or Quit. - Run Free Lou and Rest in Peace

          1981 GS550T - My First
          1981 GS550L - My Eldest Daughter's
          2007 GSF1250SA Bandit - My touring bike

          Sit tall in the saddle Hold your head up high
          Keep your eyes fixed where the trail meets the sky and live like you ain't afraid to die
          and don't be scared, just enjoy your ride - Chris Ledoux, "The Ride"

          Comment


            #6
            As Cowboy mentioned having a Dunlop paired with a Shinko might be a problem.
            Having a touring tire paired with a cruiser tire might be a problem.

            Is the new rear properly bedded on the rim? Proper tire pressure in both rims?

            I used to get a subtle front end weave when the air pressure would drop in only one of the fork legs.
            2@ \'78 GS1000

            Comment


              #7
              In my case I had shake on deceleration and handlebar shimmy on high speeds and the cause were leaked swingarm shocks. In my country most people do front forks rebuild and they completely forget the back, which often leads to crash.

              Comment


                #8
                While you're tinkering, check the swing arm for looseness. I had an old Cb750 than had the same symptoms, finally tracked it down to that.
                78 Gs 1000, 94 Honda Xr600

                Comment


                  #9
                  Wheel bearings perhaps? I had one go, replacement is pretty easy with a good blunt punch and replacement bearings are about $40 for a pair. Lift the front wheel off the ground and try to flex the wheel at the axel or whatever you call it here and see if there is any play.
                  GS550T 1981
                  GS850G 1983
                  GS650G 1982
                  GS650G 1982 Under Restoration 😳🏍👍

                  Comment


                    #10
                    Originally posted by The1970's View Post
                    steering bearings, I did replace them 6 months ago.
                    Id be curious about that project. Were the forks installed when you replaced the bearings ? How did you set the bearing torque. Might just need to be snugged up. Make sure one set of fork pinch bolts (top or bottom) are loose before you tighten the head bearings.

                    Yes. Get some new fork springs.
                    82 1100 EZ (red)

                    "You co-opting words of KV only thickens the scent of your BS. A thief and a putter-on of airs most foul. " JEEPRUSTY

                    Comment


                      #11
                      Originally posted by bonanzadave View Post
                      Id be curious about that project. Were the forks installed when you replaced the bearings ? How did you set the bearing torque. Might just need to be snugged up.

                      Yes. Get some new fork springs.
                      I basically went through the bike 6 months ago. New wheel bearings front and rear, steering bearings. Took it down to the frame except for the engine and painted most of the frame. Upgraded to the all balls bearings and tightened them with the forks out till it felt right to me; a slight drag turning side to side.

                      I planned to replace my dunlup shortly after the rear. I didn't think that would cause a bounce though?

                      Tire pressures are good and with the wheel on a truing stand it seems the rear tire bead is perfect all the way around
                      The current garage:
                      1978 GS750
                      1975 GT750M
                      1984 CB700SC
                      1982 XJ650 Seca Turbo
                      1975 RD250 - 350 conversion

                      Comment


                        #12
                        Well looks like I was wrong to begin with. I ended up tightening up the steering bearings and it got rid of most of the shake. I still get a little shake every once in a while but it's so little that it's hard to tell if it's my bike or the road. What causes the head bearings to come loose? Or is it just wear and you have to tighten them every so often?
                        The current garage:
                        1978 GS750
                        1975 GT750M
                        1984 CB700SC
                        1982 XJ650 Seca Turbo
                        1975 RD250 - 350 conversion

                        Comment


                          #13
                          Originally posted by Mr.humbucker View Post
                          Wheel bearings perhaps? I had one go, replacement is pretty easy with a good blunt punch and replacement bearings are about $40 for a pair.
                          I know Canadaians pay a lot for some things, but that's 250% of what we pay here. Local bearing shop has them at $8/each
                          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


                            #14
                            Maybe I should move there ... the point is they're a relatively cheap and easy fix whether they're $16 plus tx US or $40 Cnd a pair ($31 USD). Good. To hear the problem is solved for the vibration.

                            Big T - what model of GS850 1981 are you offering up in your signature block for a project?
                            GS550T 1981
                            GS850G 1983
                            GS650G 1982
                            GS650G 1982 Under Restoration 😳🏍👍

                            Comment


                              #15
                              " Make sure one set of fork pinch bolts (top or bottom) are loose before you tighten the head bearings."

                              Dang me, I failed to loosen one and was unable to figure out why my head bearings seem so tight. (I had a slight low speed handlebar wobble.) Today, I corrected my error and wobble was gone. Thanks!
                              1981 gs650L

                              "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

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