high speed wobble



14 replies to this topic
  • stoner

Posted May 27, 2002 - 05:00 PM

#1

While riding yesterday I finally got up the guts to open the 426 up on the dirt road leading into my favorite riding spot.From 4th gear on the front of the bike started to fell very light and unstable,almost like a wobble.Has anyone else experinced this and if so what is the problem?I tried adjusting my body positioning so that I had more weight over the front wheel and this seemed to help alittle but did not cure the problem.I checked the rear wheel alaignment when I got home and it was dead on,I checked the tire pressure and it was 12.5psi just like I usually run.Do I need a steering dampner or could it be something else?Any help would be appreciated as this was unnerving to say the least!

  • yznvegas

Posted May 27, 2002 - 05:14 PM

#2

Is your front wheel true?

  • thumper4life

Posted May 27, 2002 - 05:21 PM

#3

steering dampner would possibly help, try raising the forks up in the top clamp a few millimeters. possibly the bike is not suspended for your weight

  • Fireballsocal

Posted May 27, 2002 - 06:23 PM

#4

A steering dampner will help but you can tune most if not all of the bar wobbles out with suspension tuning. I must disagree with thumper4life. Lower your forks flush with the top triple clamp. This will increase your high speed stability and your wheelbase. This will cause the bike to turn a tad slower but it's gonna be a tradeoff. Next, drop two clicks of compression on the forks. You want the suspension soaking up most of the bumps in the road instead of transferring them to the bike. This should cure the problem for the most part. If your rear tire starts to get real "busy" with these settings, you can try dropping a click or two of the compression for it as well.

  • stoner

Posted May 27, 2002 - 08:08 PM

#5

Yes the front wheel is true,the forks are 3mm shy of flush,and she still wobbles.You are right it probably is the suspension.I can't afford to get the suspension done right now so any suggestions for settings are appreciated.Let me give yoy my particulars-I am 6'04"and weight approx.220.I ride mostly in the sand pits by my house.I ride mostly on the small mx tracks that we (me and the other 50 guys that ride here have made.It is fairly loose sand with some fairly solid patches.Quite a few small jumps and a couple doubles.I am a novice class rider who wants to be an expert(am working on it)I have set the sag at 100mm-and I am currently running my forks at:
Compression:7 clicks out
Rebound:9 clicks out
My sag-100mm
Shock
Hi compression1-3/8 turns
lo compression:8 clicks out
rebound 12 clicks out
These are the settings that were recommended by MXAction.
Do these sound appropriate?I found that these settings improved the handling of the bike on the practice tracks but weren't so good on the trails getting to the track(more unstable)I know this was long winded but I am very interested in learning how too tame this 426 BEAST,as I am fresh off the very tameable CR125(2001)and any info and/or advice would be greatly appreciated.
Thanks

  • John_Lorenz

Posted May 28, 2002 - 02:50 AM

#6

Head shake, speed wobble are two completly differant issues.
Before YZ-nLimbo goes off I read the thread moron.

What you experianced is head shake, My 00 has the same, others have the same. Do a search on the subject there are some good posts.

Proper setup of the front and rear Suspension SAG, Decomp, Comp and fork height in the trees can help eliminate it but not completely. Make sure the sag is set to 100mm (Period) and drop the forks in the trees about 10mm. This should help some. Dropping the forks will cause the forks to become more stable in the clamps (Not as Long) think of it as choking up on a bat swing is shorter and the pendulum effect is lessened. This also will cause the front to drop and force the back end to be more suseptable to speed wobble, shortning the wheel base.

It is a trade off you have to experimant to establish you style setup

The Dampner is another way to go ...

Geez yznLimbo is the Wheel True ? Thats a answer from a real expert alright :)
xoxo and lottsa love to yznLimbo
ego

[ May 28, 2002: Message edited by: EgoAhole ]

  • yznvegas

Posted May 28, 2002 - 04:27 AM

#7

Hey Egodumbhole, if the wheel was bent it would cause all kinds of problems, including a high speed wobble. So it looks like you are the moron. My girlfriend teaches first grade if you wan't some lessons on proper punctuation. You destroying the english language is hard on my eyes. Have fun typing posts all day. Oh yah, when DO you ride?????

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • John_Lorenz

Posted May 28, 2002 - 04:44 AM

#8

Its amazing you have a girl friend I figured you were still nursing

XoXo
Ego
Keep it coming DimWit

Oh yah, when DO you ride?????

Why ya gonna call me out after school, or ohhh tell on me or better yet Put me in a wall
Hahahaha another bug in the web :)

Read Below halfWit

[ May 28, 2002: Message edited by: EgoAhole ]

  • 98yz

Posted May 28, 2002 - 05:57 AM

#9

Ego, are you sure bout raising the forks in the clamps. Everything I have read says raise the forks in the clamps for cornering and risk headshake at speed; Lower the forks for high speed stability and sacrifice turning. How come you guys are running 100 mm of sag? I have mine revalved with stock spring rates and run 95 mm of sag. I am 6'2" 200 lbs. Intermediate level motocrosser. The bike works very well in the woods also.

  • John_Lorenz

Posted May 28, 2002 - 06:03 AM

#10

I could be wrong ? but the speed wobble would come from a shorter wheel base to compinsate for the wobble you can add a link to the rear and adjust.

The further down the tubes are in the clamps (Lowering) will lesson the flex of the front end hence eliminating the Head shake.

If I am wrong then thats the reason I get into those nasty tank slappers :D :)

Your sag is what you use, prefreance, I just used it as a starting point sorry for the confusion.

[ May 28, 2002: Message edited by: EgoAhole ]

  • Mark_Cantrell

Posted May 28, 2002 - 06:58 AM

#11

I have to agree with Fireballsocal.

When I run fast on loose dirt, my front end feels light, disconnected, and sways back and forth. This is nothing like head shake. When I get head shake (usually landing nose first hard), the effect is more like Churchill's description. Brutal, hard, and short. It is violent. Can go lock to lock. Nothing like the 'float' described here.

Tune it out. If you ride MX or SX, get the high speed stability of more rake. Lower the forks in the triple clamp (or make the fork legs longer, or raise the triple clamp higher on the fork). On the MX track, you don't steer as much with the bars anyway. That is for low speed tight stuff in the woods. If you need the tight twisty stuff, raise the forks in the TC (or make the legs shorter or lower the TC on the fork) and get more float or headshake.

Actually, I can cut down on the headshake tendency with more rake but I don't know if it will help the float or not. Any tuners?

Good luck,
mwc

  • John_Lorenz

Posted May 28, 2002 - 06:59 AM

#12

Some one likes me they really really like me :)

  • John_Lorenz

Posted May 28, 2002 - 07:11 AM

#13

Hey brian

can we get a tip session for the head shake / speed wobble from the MX-Tech expert John Curea online ?

I think it would be a good thing for all of us to gain a pro pespective.

  • Mark_UK

Posted May 28, 2002 - 07:56 AM

#14

i know it sounds daft but are your forks balenced
same level of oil in each rebound and compression clickers the same?
and is the tripple clamp/ forks / front wheel spindle all true without being twisted up.

at the end of the day,,, cud be worse,, cud be a ktm

  • Shawn_Mc

Posted May 28, 2002 - 08:08 AM

#15

If it was a KTM, it wouldnt shake! It wouldnt turn either :)

One way or the other, you need to add some rake to get rid it the vaguegaries in the front at speed. If your compression setting the front is on the soft side, it will add to this, I believe. Not matter which way you go, its a trade off, unless you buy a damper.





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