front tire hop issue

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by NHKTM990, Oct 26, 2013.

  1. NHKTM990

    NHKTM990 Been here awhile

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    OC-ers,
    Have a 2012 990 Adventure R and love it. Since purchase I have noticed an up and down hop or pulse in the front end between 30-42mph. Dealer re-tourqued the head, no change, just got the new front stocker replaced under warrant yesterday, no change.
    Mechanic (who seems disinterested at best, or actually annoyed) and now says the rim has a dent in it. You can see it but it is subtle and no sign iof high impact on rim edges.
    Im thinking that the rim has been tacoed since the beginning and he either didnt say, or didnt notice. Anyone have similar probs. There is no head shake even when it is pulsing. and it is stable at high speed.
    I am hoping that KTM keeps doing the right thing, I think Im do a new rim. Thoughts?
    #1
  2. pdxmotorhead

    pdxmotorhead Long timer

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    Ick,, thats going to be a he-said she-said issue unless the dealer is really behind you..

    Good luck!

    Dave
    #2
  3. gearheadE30

    gearheadE30 Long timer

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    I mean, I've bent mine and hammered it back into round as best I could... as long as the wheel is balanced reasonably well, it doesn't really seem to make much difference. Without the weights, I had hopping at similar speeds, and the steering would get wobbly much above highway speeds.
    #3
  4. SCflyer

    SCflyer Long timer

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    You're not alone. Mine does it too. If I recall it's been discussed before and some blame the tires so switch and say it's better or fixed. I put a new OEM on the front and same thing. I may just deal with it for a while or maybe put a TKC80 on and have from a trip a while back. I don't recall any noticeable bounce with it like the stock.

    Advise of a solution if something works for you.
    #4
  5. SCflyer

    SCflyer Long timer

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    "The front end had an annoying hop around 35 mph - reported as somewhat common on the Internet. The balance is good and so is the run-out. Have read the Pirelli Scorpion can sometimes be like that. Replaced with a TKC-80 resolving the hopping issue and giving good gravel road traction."


    Found this in my search so one support for the change...

    Googled - https://www.google.com/#q=ktm+990+front+tire+hop+

    Look down about 4 posts and there's a couple threads on here from a couple years ago.
    #5
  6. viverrid

    viverrid not dead yet

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    At between 30 & 42? Ride faster or slower!
    #6
  7. ADVill

    ADVill Been here awhile

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    Scorpion
    #7
  8. Zuber

    Zuber Zoob

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    Don't do anything until you try a different brand of tire. The front Scorp 90/90-21 tire has had issues for the last 4 years or more. There's a good chance you've got two bad tires in a row.

    My 2010 had a bad tire from the factory, it was round in the center, but the tread was not on straight and would cause a wobble when leaned over. It was worse when the pressure was lowered to 25 psi, not bad at max pressure (35 psi?).

    It's winter now, good time to try a TKC-80 front.
    #8
  9. NHKTM990

    NHKTM990 Been here awhile

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    What Type Of Tools Did You Use To Pound The Wheel? Any Special Body Work Hammers Or Anything?
    #9
  10. BigNastybrp

    BigNastybrp Big Nasty

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    it will make it weaker just ride it.
    #10
  11. Zuber

    Zuber Zoob

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    I've straightened some light dents out. When you buy new rims, they are rarely perfectly true. Often, the welded part is twisted and the whole rim is taco'd. This is difficult to true using the spokes alone. You MUST pull the wheel down to work on it.

    I have a band saw and a lot of maple wood. I've made supports to focus the hammering to exactly the right spot. Then use a 5 lb dead blow. It's easy to make it worse. Haven't had much luck using a press.

    I'll lay the rim on my weld table (5x5 ft and 3/4" thick steel) to check it. I clamp it down and use a long pry bar to move it around. You can't fix every dent, many are too bent and will crack when straightened.
    #11
  12. oddshapedballs

    oddshapedballs n00b

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    I've exactly the same issue on the same year (2012) mine is worse at 35 - 42 mph. So far I've had 2 new Scorps on the front and now on a full set of Conti Attack Trail 2's.
    The dealer's had the bike back 5 times over the last few weeks, they've checked everything suspension wise and swear after 2 mechanics and the dealer himself rode the bike that there is no problem???

    I'm starting to wonder of it's a fueling issue and the bike hunts where it's running lean in the mid-range, and as such, maybe a Power Commander or something would maybe sort it out.
    My old GS used to hunt a bit which made it jolt forward a bit at certain revs in certain gears and with the soft suspension on the KTM I wondering if the jolts I felt on the GS are hops on the KTM.

    Going to get an independent second opinion and if it can't be sorted it'll go!
    #12
  13. HellsAlien

    HellsAlien a has-been that never-was

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    In my experience with the bike (950A since late '04) the vibration you guys are experiencing is happening at what is called the fundamental first frequency of vibration of the front end assembly (the forks/sliders w/wheel assembly).

    The excitation comes from out-of-round tires (typically Skorps), tires not seated fully on the rim, dented front rim, out of balance front wheel assembly, or a combo of all of these. Start by looking at this stuff.

    If you feel pulsation back into the front brake lever check the brake mount tabs on the hub for axial runout, should be less than .002".

    On long straights, I have stood up and watched the front wheel go back/forth in the forks at the right (or wrong!) speed in sync with the vibration I could feel through the bars. Can sometimes even see the out-of-round on a bad Skorp (be careful doing this for obvious reasons!)

    The worst I had was a out of round Brazilian Skorp on a dented stock rim with a bent hub (almost forgot that part). Had to toss the tire and have Woodys flycut the brake mounts on the hub, they had axial runout of .005".
    Where this runout came from was a mystery as I had not crashed the bike, only a slow mud-clogged front tipover north of LaPaz in construction zone.

    The best was a Conti Trail Attack on a Woodys-assembled 1.85 Excel front with the HD spokes. The Conti is well made tire and stiffer carcass/compound than the Skorp, this pushes the tire vibration frequency up, maybe out of the realm of the front end, hard to say.

    Hope that helps more than confuses! :D
    #13
  14. ride-for-life

    ride-for-life Been here awhile

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    Yes when scorpions wear they wobble the bars at speed been throw that. But what sounds like is wrong is your wheel is out of true out of round up and down not left too right find a good wheel smith and problem should be solved. I had the same problem a few years back about the same speed your talking about and the wheel was out of round.
    #14
  15. GLRRA47

    GLRRA47 Adventurer

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    My OEM Scorps were fine. Mounted Heidenaus and had issues as you describe. Rode Ohio to Colorado and back - no issues at speed. Figure it'll likely go away with a new tire.
    #15
  16. ultimatezap

    ultimatezap Adventurer

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    I had 908's on my Baja. Had head shake at 65 or so. Went to Scorp MT 90's. Shake gone, but now had the up down pulsing, similar speed to you. Sent the front back and bought another of the same. Hop gone, Pirelli covered the return, refunded my $. I'd try another.
    #16
  17. gearheadE30

    gearheadE30 Long timer

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    Nothing special. This isn't all on the 950, but I've used a vise, dead blow hammers, a 5 lb hammer with a block of wood and a rag, and a press with varying degrees of success. It really depends on how it is bent, and as has been said, it is easy to make it worse. You also have to make absolutely sure that the rim is properly supported when pounding on it, or you can easily bend the wrong section of the rim.
    #17
  18. NHKTM990

    NHKTM990 Been here awhile

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    Thanks for all the advice! Ill have a go at it with a dead blow, my torch and a little patience. It is really a minor dent with no chip or crack in the lip of the rim so I think it will be a simple fix. Worse case scenario is I frag the thing trying to fix it and buy a new, aftermarket for the deuce. Best time of year to fix things, riding seasons about over. Time to start breaking stuff on my sleds!:rofl

    This is a very helpful site BTW. Love the OC Nation!
    #18
  19. Bandit33

    Bandit33 Adventurer

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    I had a similar situation on my 2012, the dealer (who was very helpful) wound up sending the front wheel to a local wheel shop. They trued up the wheel and it did way better.

    Don
    #19
  20. NHKTM990

    NHKTM990 Been here awhile

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    I am getting similar service from my dealer, Ken's Yamaha of Norway Maine. He justed e-mailed me and said although KTM does not feel the rim could have had a perceivable dent from the factory, they are going to pay to have it trued up. That seems like a fair resolution. so far, a new front tire and a trued/repaired rim at no charge. No complaints here!
    #20