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Thread: front end wobble in turn on airhead

  1. #1

    front end wobble in turn on airhead

    hey, i was out riding the 84 R65 over the weekend up in Shenandoah. the bike ran fine, but i noticed when i leaned over in the sweepers on 211 near Skyline Drive doing about 50 mph, that a wobble would be induced at the more aggressive lean angles. the pavement appeared smooth, anyway it was consistent in all turns, so i am discounting road irregularities.

    what suspects should i be looking at here? tires? uneven fork fluid? to much too little fork fluid? bad steering head? just wonder what the usual suspects are.

    any help appreciated!

  2. #2
    Sir Darby Darryl Cainey's Avatar
    Join Date
    Mar 2003
    Fenwick, Ontario Canada
    My first guess is the steering head bearings.
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  3. #3
    wasn't but four years ago those steering head bearings were rebuilt (not cheap). i will check the torque on them and see how that is. and run the shake the forks test with someone holding the handle bars stiff. maybe the original install did not hit the torque correctly or it has loosened.



  4. #4
    Registered User
    Join Date
    Sep 2003
    Virginia Beach
    I'd check the front wheel bearings...

  5. #5
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    How old are the tires? You might have some uneven wear near the edges that you get into when making the sweeping turns. This pulsing input will tend to upset the stability, especially if the steering stem bearings are marginal. Check tire pressure, too.
    Kurt -- Forum Liaison ---> 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!

  6. #6
    Quote Originally Posted by 76754 View Post
    wasn't but four years ago those steering head bearings were rebuilt (not cheap). i will check the torque on them and see how that is. and run the shake the forks test with someone holding the handle bars stiff. maybe the original install did not hit the torque correctly or it has loosened.


    Standard procedure when replacing head bearings. Run it a few hundred miles then check for slack. Continue until you know they are seated.

    Easy check. Riding straight, hands off bars, 25-30 mph. bunp the hand grip to see if you can initiate a wobble. If yes, head bearings loose. Just sinch them up a bit and try again.

    Head bearings too tight and high speed weave will raise it's ugly head.

  7. #7
    John D'oh
    Join Date
    Aug 2006
    Close to Fort Worth Texas
    I support tire pressure as a possible culprit and perhaps swing arm bearing tension too. How are the shocks? Are they set the same? Something is causing the bikes steering geometry to change when the suspension is loaded in a turn and there are several reasons for that to happen. Worn shocks / shock rubber steel mounts. Add worn out fork springs and it might be excessive 'squat' changing the trail.
    Have you noticed a wobble around 40mph as you decelerate from 50 or higher straight up? How do you overcome the wobble when you are in the turn? Acceleration or brakes? Change the angle of the lean or just hang on and pray?

  8. #8
    Registered User krpntr's Avatar
    Join Date
    Jan 2010
    Mt Vernon WA


    I used to have similar symptoms on my '82 R100. I tightened the steering head bearings and installed new bushings in the rear shocks. Under the seat, the brace that crosses the frame just aft of the tool box sometimes separates from the frame. (I saw this on two bikes and both had a wobble.)

  9. #9
    Registered User toooldtocare's Avatar
    Join Date
    Mar 2008
    DeLand Florida
    Quote Originally Posted by DARRYL CAINEY View Post
    My first guess is the steering head bearings.
    My guess too. Simple and cheap to check.


  10. #10
    Minnesota Nice! braddog's Avatar
    Join Date
    Jun 2003
    Twin Cities - MN
    Bearings, yes, but even simpler is to check your tire pressures. Also, put the bike up on the centerstand, look straight down at the front wheel and spin it. You can then see the wear patterns on the front tire. You may have some cupping going on.
    Brad D. - Member #105766
    '77 R100RS - Black Beauty (big pipe, baby!)
    '94 R1100RS - Sylvia

  11. #11
    these are good suggestions and i will implement them and report what fixes the problem. because fixing the problem has to be a part of the future for me and the R65.

    currently i solve the problem by easing off the throttle and straightening up the turn and the wobble goes away. if i had an aircraft Artificial Horizon installed i could probably report the exact angle of lean where the problem arises. it is just at the beginning of a normal lean transition into a strong lean.

    i am not getting any wobble on regular braking straight up.

    i will report and any other suggestions for my checklist appreciated. i hope to have the bike sussed out by Rally time, because i need a new rear tire and hope there are some deals up there. Vermont was a bust for tires at the rally, and I did not make Redmond. i will run the k75 if this isnt fixed by rally time.

  12. #12
    When is the last time you did anything w/ the fork oil?
    How do the bottoms of the forks look? Any build up? Clean/dry?

    Just sitting they may not leak... Under load you could be losing some.

    Worth a look.

  13. #13
    Rally Rat
    Join Date
    Feb 2009
    Chicago, IL
    Another easy check: Make sure your pinch bolts on the axle are tight. If not they can cause a situation similar to the one you describe.

  14. #14
    I hope you let us know how it turns out.

  15. #15
    Do yourself [and us] a favor. Change or adjust 1 item at a time then test.
    That way you can be sure to identify where the problem lies and educate yourself and us.
    I usually try to start with the easiest things first. Tire pressure, loose bolts in the rear, frame / shocks, steering brngs.
    I vote for pressure, or bearings, but many say a wobble in the front points to a component in the rear.
    Please keep us posted.

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