1983 R100 Front End SHAKE & SHIMMY

Discussion in 'Airheads' started by SELDOMSEEN, Jan 30, 2013.

  1. SELDOMSEEN

    SELDOMSEEN Proud Infidel

    Joined:
    Jun 9, 2004
    Oddometer:
    129
    Location:
    MAINE, Connecticut
    I know were not supposed to let go of the handlebars but if I do :eek1 at 38mph and higher my front end will shake so bad it would crash if hands are not immediately back on the bars. I've had it to a great dealer but they could not solve the problem. No bent wheel, no bent frame (I think, not sure on that), anyway, any ideas at all would be very appreciated. :ear

    Thank you.
    #1
  2. 100RT

    100RT Been here awhile

    Joined:
    Nov 4, 2009
    Oddometer:
    846
    Location:
    N. E. OHIO
    Sounds like the steering head bearings need adjust a bit tighter.
    #2
  3. disston

    disston ShadeTreeExpert

    Joined:
    Mar 22, 2011
    Oddometer:
    10,640
    Location:
    Silver Spring, Md
    I would check that the bearings were tight and if not found to be loose or tightening doesn't help I'd probably replace them right away.
    #3
  4. Rapid Dog

    Rapid Dog bikes, booze, broads...

    Joined:
    Oct 28, 2003
    Oddometer:
    9,807
    Location:
    Strangel Living West of Hell, SoCal
    ...head bearings are the first thing to check.
    Quick test is to pull the bottom of the forks back and forth while on the centerstand.
    #4
  5. Brun

    Brun Been here awhile

    Joined:
    Jun 29, 2012
    Oddometer:
    263
    Location:
    BorderBurg, South East Oz.
    My old girl got the front end shimmies when a rear wheel bearing spun in the hub. Worth checking.
    #5
  6. Rapid Dog

    Rapid Dog bikes, booze, broads...

    Joined:
    Oct 28, 2003
    Oddometer:
    9,807
    Location:
    Strangel Living West of Hell, SoCal
    ...oh and good point, also check the swingarm bearings...
    #6
  7. mykill

    mykill odd

    Joined:
    Feb 6, 2008
    Oddometer:
    1,169
    Location:
    Los Angeles
    Put it on the centerstand and start checking. Grab the bottom of the forks and move back and forth and side to side feeling for roughness or notchiness or binding. Anything other than buttery-smoothness is unacceptable. Push on the sidewall of the front tire at the top feeling for wheel bearing play. Feel the tire tread with your open hand.. Cupping? odd wear? Grab the rear wheel at the back and push side to side checking S/A bearings. top and bottom for wheel bearings. Straddle the bike off the centerstand and dive the front end. Clicks, clunks? Rise should be slower than dive. Bounce your ass on the seat... Pogo? weird noises?
    #7
  8. craydds

    craydds Long timer

    Joined:
    Aug 3, 2010
    Oddometer:
    1,170
    Location:
    Las Cruces, NM
    + 1 on all the above, especially the CHECK EVERYTHING. That also inclues:
    check rear shock upper and lower bolts - TIGHT?
    rear suspension SAG - measure and set correctly
    front suspension SAG - ditto
    front to rear "attitude" - nose down? nose up? level?
    front fork alignment
    all front end (triple clamps, axle, pinch bolts, etc.) - TIGHT!
    that is a start - get to work
    #8
  9. Bigger Al

    Bigger Al Still a stupid tire guy

    Joined:
    Oct 12, 2004
    Oddometer:
    8,029
    Location:
    Auburn, CA
    My R90 has always gotten the shimmies in the front end when the front tire is down to about 25% left on the tread. Brand of tire has never made any difference.
    #9
  10. craydds

    craydds Long timer

    Joined:
    Aug 3, 2010
    Oddometer:
    1,170
    Location:
    Las Cruces, NM
    Clean, inspect, and grease those steering stem bearings. Now, it is the time to inspect your top plate. Is it the flat stamped steel plate? Inspect it, toss it in the trash and get a ToasterTan.
    #10
  11. boxerboy81

    boxerboy81 Stay Horizontal

    Joined:
    Jul 22, 2009
    Oddometer:
    2,749
    Location:
    Melbourne, Oz
    All the above...and check your tyre pressures too.
    #11
  12. supershaft

    supershaft because I can

    Joined:
    Sep 9, 2010
    Oddometer:
    9,116
    Location:
    San Francisco Bay area
    Did anybody mention the tires themselves? They can do it too. The worst thing about it is even a perfect setup will still do that sometimes around that speed no matter what. Some guru's claim that they can tune a bike to be absolutely shimmy free. No they can't. No one can because such a bike does not exist.

    In my experience if it isn't the steering head bearings, it's a toss up between the wheel bearings and sticking forks. After that on a less frequent basis I have seen it been all the above mentioned things and then some.
    #12
  13. craydds

    craydds Long timer

    Joined:
    Aug 3, 2010
    Oddometer:
    1,170
    Location:
    Las Cruces, NM
    + 1. So true. If you study and learn all the suspension set-up stuff, and work really hard on your bike to make sure everything is "perfect" ( and spend the time and $$$ ) , it is still a motorcycle and the laws of physics still apply. One more thang - we can make these old machines handle very nicely; we can NOT turn our vintage bikes into a CBR600RR.
    #13
  14. ozmoses

    ozmoses Ride On

    Joined:
    Jul 3, 2009
    Oddometer:
    4,989
    Location:
    USA
    The Shimmyshake!

    SS- we've discussed this before.

    I've checked, double checked and re-checked everything mentioned; mine still shakes right around 35-40 as you describe.

    What I have not done is remove the Progressive(brand) fork springs I installed just before the shimmyshake began. I am being stubborn & probably stupid about it ,but may finally change my mind come Spring...

    So, how are your fork springs?
    #14
  15. supershaft

    supershaft because I can

    Joined:
    Sep 9, 2010
    Oddometer:
    9,116
    Location:
    San Francisco Bay area
    I suspect taking them out might fix a part of your issue. Those springs do not have enough sag. They are too stiff and too stiff increases stiction and stiction causes shimmyshakes. I have fixed the shimmyshakes more than once before by removing Progressive springs. My stock springs with a little additional preload work WAY better. I am just telling it like I have seen it but I ride my airheads harder, brake them deeper and jump them further than anyone I have ever rode with and those Progressives are WAY too stiff for me. IMO they cause stiction, chatter, and shimmyshakes besides not offering enough sag to start with and being just too stiff.
    #15
  16. Houseoffubar

    Houseoffubar fine beer sampler

    Joined:
    Dec 4, 2010
    Oddometer:
    1,824
    Location:
    Bothell, Washington
    I'll throw in another for tires. I put a new front Metzler on a customers Kawasaki Concours, and it tank slapped violently, from 50, down to 25, any time you held on lightly, or let go of the bars.
    I replaced the tire with the oem...no shake at all.
    #16
  17. chasbmw

    chasbmw Long timer

    Joined:
    Feb 19, 2006
    Oddometer:
    2,411
    Location:
    Bath Uk
    Shimmy at 30-40 mph is most likely to be the headstock bearings. The simple initial fix would be to clean and regrease the bearings and readjust.

    How do you know when your bearings are too tight? The bike will tend to roll from side to side, keep adjusting the bearing until you remove the roll but not so loose that you have reintroduced the shimmy.

    If you fit new bearings they will settle into position over the first 1000 miles, so you will need to keep readjusting them.

    Don't use old manual tyre pressures, modern tyres work best with pressures in the mid 30s front, high 30s rear.

    Avoid Metzler tyres as marketed for airheads.
    #17
  18. ME 109

    ME 109 Long timer

    Joined:
    Jun 25, 2009
    Oddometer:
    3,350
    Location:
    Albury Australia
    Now we're talking.:D

    Why does your broken shock mount spring to mind?
    #18
  19. Rob Farmer

    Rob Farmer Long timer

    Joined:
    Aug 27, 2002
    Oddometer:
    5,945
    Location:
    Loughborough, Leicestershire. England
    I've always found the biggest cause of these issues on the twinshocks to be wheel bearings that are incorrectly shimmed or bearings that haven't been shimmed for years.
    #19
  20. Moonshiner

    Moonshiner aka "B-dog"

    Joined:
    Feb 1, 2008
    Oddometer:
    183
    Location:
    Twin Cities of Minne-snow-tah
    I can't add much to what's already been said here. But for me, it wasn't the steering head bearings. I bought my first '77 and rode it awhile before fixing or changing anything. I noticed a shimmy at about 35-40. Just in that range. Checked my front tire, it was cupped. Back tire was fairly worn and squared off. Rear shocks and front springs were original. Put on a pair of IKON's on the rear, adjusted for my bulk. Put Progressive springs on the front. Installed 2 new Metzelers. The thing rode then, and still does, like it's on rails. I have adjusted my steering head bearings over the years as well, and ALWAYS keep an eye on tire pressure.
    #20