Front End Wag?

Discussion in 'Thumpers' started by meat popsicle, May 24, 2005.

  1. GMM

    GMM Been here awhile

    Joined:
    Mar 15, 2005
    Oddometer:
    100
    Location:
    Middle Tennessee
    Here is something to consider. I had a Kawasaki Concours that would headshake on decelaration between 40 and 45 mph if I didn't have a firm grip on the handlebars. The oscillations would progress to the point of a tank slapper if I didn't grab hold of the bars tight. After alot of head scratching I finally found the stearing head was loose. The kicker was that there was no play in the front end using the grab the fork and try to wiggle back and forth test method. I ended up tightening the steering bearing cone about a quarter turn and all was good. You may want to tighten the steering head up a little more and try it again. Remember you need to loosen the top clamp fork pinch bolts, and the steering head pinch bolt and tighten the steering stem bolt. You may want to grease the head bearings first to take that variable out, and also you may want to preload the steering stem nut (tighten it so you can't turn the front end) then back off until the front turns easy without play. If I had this problem this is what I would try first. I have had some front wheels horribly out of balance, they would make the front hop up and down, but not headshake. Another thing I would check is the rear suspension sag to see if it is in spec. Good Luck.

    Greg
    #41
  2. AusieRob

    AusieRob Just Gas It!!

    Joined:
    Aug 19, 2004
    Oddometer:
    377
    Location:
    San Francisco
    Yep, that's good advice....
    #42
  3. meat popsicle

    meat popsicle Ignostic

    Joined:
    Feb 9, 2004
    Oddometer:
    14,567
    Location:
    Circumlocution Office of Little Dorrit
    Thanks for the info - just curious why the additional steps? alignment? :ear
    #43
  4. GMM

    GMM Been here awhile

    Joined:
    Mar 15, 2005
    Oddometer:
    100
    Location:
    Middle Tennessee
    If you don't loosen up the fork clamps and the top clamp pinch bolt, you will not be tightening up the bearings. You will just be tightening up the steering stem nut. Also if you were to just loosen the top clamp pinch bolt and not the fork pinch bolts, it could put everything in a bind. Here is how I adjusted my adventure's front end when I greased the steering head bearings:

    1. Loosen fork pinch bolts on the top clamp and top clamp pinch bolt. (You have to take the handle bars off to get to the steering stem nut.)

    2. Crank down the steering stem nut until there is drag on the forks go easy here or you will screw up the bearings. (You are preloading the bearings here I think the manual may give a torque spec on this, but I may be confused with another bike.)

    3. Back off on the steering stem nut until the forks turn freely with no binding, and no play when you wiggle the forks back and forth. There is a fine line between having it too tight and too loose. Turn the forks lock to lock to make sure there is no binding throughout the range of movement.

    4. Once satisfied with the adjustment, torque the top clamp pinch bolt to spec, then torque the steering stem nut to spec., then the fork pinch bolts.

    5. Go for a ride.

    If you are going to go to this much trouble; and you haven't done so already, go ahead take the front end apart and grease your steering head bearings. Check out the components for damage and wear. They may be bad, and causing you problems. Let us know when you get her fixed, and what the problem was.

    Greg
    #44
  5. meat popsicle

    meat popsicle Ignostic

    Joined:
    Feb 9, 2004
    Oddometer:
    14,567
    Location:
    Circumlocution Office of Little Dorrit
    Just a note as I haven't had time to dig into the more complicated suggestions offered here. As stated previously I aired down to 25psi cold F/R which seemed to help a bit. And on uneven pavement in a lane change or corner the front end didn't seem to "get going" with that oscillation. It wiggles but it doesn't grow or require that I try to correct it.

    Well I found out that moving around on the seat does start an oscillation. Just slipping up or back, which requires me to lift up off the seat and then come back down starts the oscillations; and I don't have to be in a lean or corner or on uneven pavement to help. So I think at this point that Stephen, thinkin' about the butt, may have been correct to get metaphysical on my arse... :D

    Seriously, I lift up, shift forward (more so than back which takes weight off the back wheel no?) and plop down and the front starts to oscillate. No tank slapping mind you, this is at 80mph.

    But the speed does make me wonder about the tires and if this would be occurring with the Sahara 3s. Can nobs cause this phenomenon? Well it didn't happen right away (fresh knobs) but now that the rear is worn some and flattening out (not enough turning... side knobs look mighty fresh) could this also be a factor along with rear suspension setup?

    I am still going to try the suggestions (especially since they involve maintenance I need to do, just wanted to post that new observation.
    #45
  6. Reformed DucFlogger

    Reformed DucFlogger Inventor Of The Wheel Mk2

    Joined:
    Jul 17, 2003
    Oddometer:
    1,497
    Location:
    Peoples Republic Of Canuckistan
    ...may be too simplistic, but did you do anything odd to the rear pe-load? I've known some Duc riders who'd dropped the rear spring tension and then get the front a little too light as a result.

    Here's another wild hair, air in the forks screwing with front-end handling? I'm grasping here, but...
    #46
  7. meat popsicle

    meat popsicle Ignostic

    Joined:
    Feb 9, 2004
    Oddometer:
    14,567
    Location:
    Circumlocution Office of Little Dorrit
    I will check the setup of the rear shock, shouldn't be anything weird but maybe the shop did something awhile back? :dunno

    I bleed the forks after every hard ride; thanks for grasping :D i should check the fork setup as well.
    #47
  8. ap_xr

    ap_xr Adventurer

    Joined:
    Apr 7, 2005
    Oddometer:
    13
    I noticed my Honda XR650R doing that when on the street at speeds approaching 60mph. Low in frequency but discernable left/right transitions. I attributed it to the huge front fender acting like a sail in combination with the DOT knobbies (balanced front Dunlop 606's). Don't know for sure what it is though since oscillations can be the result of a complex, and sometimes nonintuitive, dynamic process.
    #48
  9. braaap!

    braaap! Long timer Supporter

    Joined:
    Mar 16, 2005
    Oddometer:
    4,163
    Location:
    Here and There
    #49
  10. meat popsicle

    meat popsicle Ignostic

    Joined:
    Feb 9, 2004
    Oddometer:
    14,567
    Location:
    Circumlocution Office of Little Dorrit
    #50
  11. Wannabeeuro

    Wannabeeuro Tuner chic

    Joined:
    Feb 20, 2006
    Oddometer:
    2,001
    Location:
    Boulder
    Hey Experts,

    Just read this entire thread after a buddy pointed out that I wobble over 70 MPH. I had forgotten that my bike does it as I have gotten used to it and my techique is to slide my ass back on the seat whent it starts to wobble and it stabilizes. Just wondering if Meat ever came to a conclusion on this. I have a pretty worn out MT21 on the rear and it is not balanced however I do remember that the bike did the same when it had balanced Scorpions on it which I will put back on as soon as I finish off the MT21s as I ride mostly street on the 625 ever since getting a 300 for off road.
    #51
  12. dhally

    dhally Hammerhead Supporter

    Joined:
    Feb 18, 2006
    Oddometer:
    5,145
    Location:
    Kennewick, WA
    My bike had a weave or bounce or head shake for a while. It was the worst with high front tire (D908RR) pressure, un-balanced wheels, heavy loads and wide panniers in the back and high winds. Also depending on road surface.

    Since then I've made the following changes and the wobble is completely gone under all conditions.

    - Made sure the front forks were not bound up by axle
    - Got rid of panniers and heavy loads
    - Static balanced wheels with lead slugs
    - Run abou 25 psi in front
    - Rebuilt, re-sprung and re-valved both ends (professionally)
    #52
  13. meat popsicle

    meat popsicle Ignostic

    Joined:
    Feb 9, 2004
    Oddometer:
    14,567
    Location:
    Circumlocution Office of Little Dorrit
    #53
  14. Sycamore

    Sycamore d00b

    Joined:
    Mar 30, 2006
    Oddometer:
    1,697
    Location:
    Dubai, United Arab Emirates
    chrisC, meat, loaded, all together on a nearly 4-year old thread... thought I was hallucinating for a moment.
    #54
  15. stephano

    stephano Long timer

    Joined:
    Feb 9, 2009
    Oddometer:
    2,224
    Location:
    Economically trapped in Northern CA
    I was going to say that too. Check your back end and your wheel bearings. It also easy to check a trued wheel with the the bike on the center stand. Tread design is also a culprit. I had a Michelin with one tall row of center nob's which made the tire feel weird on the street. Was happy to get rid of it.
    #55
  16. Zerodog

    Zerodog Long timer

    Joined:
    Jun 9, 2006
    Oddometer:
    1,233
    Location:
    SLC, UT
    My bike was a head shakin MOFO with Dunlop 908rrs. When I switched to 606s it went away make sure you run your Subtanks in the off position ok the highway too.
    #56
  17. badcooky

    badcooky I see dumb people!

    Joined:
    Oct 7, 2007
    Oddometer:
    1,129
    Location:
    At QLD Australia
    Headshake is so ferkin' simple to work out it's not funny, to read this is though.
    #57