Serious question. High speed wobble. Tank slapper on the way?

[Firewalker]

Hey there,
    I just fixed the previous problem of the forks being too high in the triple.  They were mashed up under the handlebars and I corrected it the other day when messing with something else.

    I also, JUST installed the sv 650 shock on the bike a day or so ago and today was the test ride for it.  

I have read that other people have had speed wobble issues and mine also occurs around 95/100.  Not too windy but there is gonna be some wind at that speed obviously.

I know the shock raised the bike in the back the predicted inch or two.  I also changed the height on the front bringing the nose back up.  Would you suspect these are the culprits?  Higher center of gravity?  The shock is set tight as a drum and I need to find a spanner to adjust it at least a couple clicks.

I tried to emulate the vibration with a very slight wiggle in the bars and sure enough she gets pretty sloppy.  (BTW:  That is the last time I test like that)  Just wondering if my adjustments would trigger this or ?  I don't detect any play in the stearing head bearing.  The bike has 10k on the clock.  I haven't checked the wheel bearings.  Just curious what you guys think.

Up to 85 she is rock steady so it's really not an issue on a day to day commute basis.  I just like a bike to be solid even when it's pegged.

Thanks in advance for any replies.   If I might add I realize 95 is not a legal speed limit so please don't waste a reply to let me know that.  Not to be an A Hole.....but I know.

Enjoy the ride.

Scott

[jeffdodge]

I just got my 98 GS last night and noticed the same today at around 90. It desperately needs new tires. Maybe that coupled with not the best asphault could be to blame?

[Deros514]

Not sure if this will help you much but it is an interesting read for figuring out why your bike does handles the way it does

http://www.sportrider.com/tech/146_0006_susp_handle/index.html

[ohgood]

I just got my 98 GS last night and noticed the same today at around 90. It desperately needs new tires. Maybe that coupled with not the best asphault could be to blame?

suspension lies with dragons. tires are hella easier to finger out (balance/new)

[ojstinson]

I don't know much about the subject but I do know that I had a consistent speed wobble with my 600 Bandit for almost a year and it completely disappeared when I put a new front tire on the bike, now I can't get it to wobble at any speed.

[tt_four]

Speed wobble is pretty much guarunteed on bikes with upright handlebars. Sportbikes are rock solid up to 180mph because you're leaning over the front wheel but when you have less weight it feels a lot less stable. I've ridden other nicer naked bikes and they do it as well. You could buy a cheap steering damper on ebay and find a way to mount it, or you could also tighten up the head bearings just slightly.

I know what you're talking about with the manually induced speed wobble, I do it on my bike all the time, partially because I kinda like the feeling, and partially because I just want to know how stable my front end is at that given speed, and it always concerns me, but I never have any problems with it when I'm not trying to do it already. Someday when I'm bored maybe I'll look into a steering damper.

It could also be helped by a worn/unbalanced front tire but there's no way to tell over the internet. Try leaning forward a bit and then doing it and see how it feels. If it doesn't do it as easily when you're leaning it's probably because of your upright riding position.

[Firewalker]

Just to clarify......My tires are pilot activs......Less than 100 miles on them and they were balanced during install. 

Will try it with some more weight on the bars.  I was just concerned that I may have done something to cause it or changed the suspension geometry by installing a taller shock.

Come to think of it/the bike has been running so poorly I would not have been over 85 until now so it may have been there all along.

Thanks for the input.

Enjoy the ride.

Scott

[gsJack]

If the bike had any hint of instability already the shock change would certainly magnify it.  Raising the read end 1-2" would steepen the steering head angle by 1-2 degrees bringing the GSs already steep 25 degree rake to 23-24 degrees, definetly getting into sportbike territory without a sporbike front end.

My GSs have both been rock steady for their combined 160K+ miles but I don't do much at those speeds anymore.  I had a nice 85 Nighthawk 650 some years ago and it had a front end stability problem.  A new front tire made it much improved but I really didn't get rid of it until I replaced the steering head bearings, they had a notchiness at dead center which was quite common with those old Hondas, replaced the head bearings on 2 of the 4 that I had.  So besides checking the head bearings for proper adjustment, they should be snug w/o freeplay, check carefully for that notchy feel at straight ahead position, feels like a bit of a detent at that position if they are going bad.

Haven't heard of any stability problems with the Activ front tire, there were a few complaints about the stability of the Demon front tire over at the Ninja 500 forum a while back.  Also make sure those new tires are both seated properly.  MC tires have a line around them very close to the rim, maybe an eighth inch or so away, that will be perfectly concentric with the rim if the bead is seated properly.  If not, reseat it.  I always chack that line before I leave my tire place after getting new ones mounted.

[black and silver twin]

make sure your tire pressures are good.

[JAY W]

Sounds like you need to soften rear shock,check all bearings inc`swing`n arm,tyre pressure.

[Lukewarm Wilson]

its your rear shock

[Firewalker]

Hey all, thanks for the input.  I know I need to adjust the preload on the shock as it was/is set to the tightest setting.  Don't have a spanner and didn't want to crush something using channel locks or a screw driver.  That does make sense about the rake angle being changed also.  It would be rare that I would ever be in that speed zone but I was wondering if it would eventually start happening at 80 then 70 and so on...

I appreciate all the replies.

Scott

[tt_four]

If you can wedge a good size screw driver in there and get it to twist I doubt you'll hurt anything more than a few scratched on the adjuster.

[JAY W]

Also taking the weight off will help (put bike on main stand) to ease adjusting.