steering
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Junior Member
Squid
Joined: Jul 2005
Posts: 11
From: chicago (wicker park)
steering
hello....i'm new to this site....i was given a '98 superhawk last week ...i just got it running the other day....and was running it hard, when i neared the red line in second..... the front end shook violently from side to side...i was told that's whats called tank slapping .....does anyone know what causes this and a possible cure? by the way i was running in a straight line when it happened......thnx in advance......standzchop
Senior Member
SuperSport
Joined: Dec 2004
Posts: 764
From: Nananimo, B.C.
Re: steering
Was the pavement smooth? did you hit some ridge in the road? Did you just drop it down from a wheelie? Did the person before you play with the bikes geometry ie: washers above the shock to raise the rear end?
Cause its really difficult to get these bikes to do that.
Cause its really difficult to get these bikes to do that.
Thread Starter
Junior Member
Squid
Joined: Jul 2005
Posts: 11
From: chicago (wicker park)
Re: steering
first..thnx very much for the replies...when i was riding it was relatively smooth blacktop....also i used a rope around the thottle to hold it at forty m.p.h. and rode without hands, the bike responded great ...as if it was riding on glue....so i think that everything is square with the front end and frame......anyways the bike doesn't show anything that looks like it's been dropped or crashed....maybe you are right about something in the road??? do you think a dampner would help this from happening again? or is tank slapping too violent to be stopped by a steering dampner?? thnx again.........standzchop
Member
Squid
Joined: Mar 2005
Posts: 62
Re: steering
I had the same thing happen to me, except was in 3rd gear and driving real hard towards redline.
Bike was stock standard fork wise and 3 weeks old straight from the factory floor.
We are not the first to have experienced this either.
I was nearly spat from the bike it slapped so hard and i nearly crapped the undies !
My belief is that this happens as the forks as possibly a little to soft and when getting very light on the front end a slight bump (and i mean slight) seems to cause this.
It doesnt happen every time either, only under real hard accel in 2nd or 3rd.
Since that happened i had new fork springs and had it revalved and have never come close to it again, I believe that this supports my theory (and it is just that) about the woeful front end.
Im sure you will find others that say it has never happened to them, but everyone of us rides differently, and every road is different.
After that first episode I was determined to get a damper, but as since the fork work it has not happened again I am happy.
Worth noting that I have also added a 6mm spacer to the rear shock and dropped the front forks 5mm... if anything was going to make this bike twitchy that would do it.
An easy fix is put in some heavier weight fork oil and you will get instant benefit.
Long term, for about $150US (cost me $180 aus) I had new stiffer springs and the standard valves re-valved and re shimmed and it feel fantastic.
Bike was stock standard fork wise and 3 weeks old straight from the factory floor.
We are not the first to have experienced this either.
I was nearly spat from the bike it slapped so hard and i nearly crapped the undies !
My belief is that this happens as the forks as possibly a little to soft and when getting very light on the front end a slight bump (and i mean slight) seems to cause this.
It doesnt happen every time either, only under real hard accel in 2nd or 3rd.
Since that happened i had new fork springs and had it revalved and have never come close to it again, I believe that this supports my theory (and it is just that) about the woeful front end.
Im sure you will find others that say it has never happened to them, but everyone of us rides differently, and every road is different.
After that first episode I was determined to get a damper, but as since the fork work it has not happened again I am happy.
Worth noting that I have also added a 6mm spacer to the rear shock and dropped the front forks 5mm... if anything was going to make this bike twitchy that would do it.
An easy fix is put in some heavier weight fork oil and you will get instant benefit.
Long term, for about $150US (cost me $180 aus) I had new stiffer springs and the standard valves re-valved and re shimmed and it feel fantastic.
Senior Member
Superstock
Joined: Jan 2005
Posts: 347
From: Western NY
Ummm....
Why has no-one recommended that he no longer uses a rope to hold the throttle steady while he rides NO HANDED!! Prit-darn-sure that will cure tankslappers in the future !
can I get a group DUH, please.
Why has no-one recommended that he no longer uses a rope to hold the throttle steady while he rides NO HANDED!! Prit-darn-sure that will cure tankslappers in the future !
can I get a group DUH, please.
Thread Starter
Junior Member
Squid
Joined: Jul 2005
Posts: 11
From: chicago (wicker park)
Re: steering
thnx, for the replies....vtrbeefa, did you use progresive springs?and how stiff did you set the front end? ..................as for darren and i'rocker maybe if you took the time to read before you answer maybe you can learn something the reason i rode no hands afterwards was to check how square the front end is to the frame and rear wheel.....cause if anything is out of whack the bike will veer to one side or the other...even if you're a little out of square you'll see the bike react...were as if you're holding the bars with your weight on them you can mask small errors.....i know my bike is in perfect line ...so that eliminates that from the reason it was tank slapping.....thnx ..standzchop
Senior Member
SuperSport
Joined: Mar 2005
Posts: 758
From: Laurel, MD
Rear suspension (probably preload) too soft or too much weight transfer to back. Bad wheel or tire or wheel bearings. Fork oil gone or low. Steering bearings. Loose axle.
In that order. It's not a common problem with a good-condition Superhawk.
In that order. It's not a common problem with a good-condition Superhawk.
Member
Squid
Joined: Jul 2004
Posts: 48
Re: steering
The rope trick, while not what I would call an entirely sane idea, wouldn't have contributed to his tank slapping, if anything it would have reduced the tendency. Often its the 'harmonics' induced by the weight of our arms, and our grip, that gets tank slapping going out of control, like that 'galloping girdy' bridge that they show in the old news reels of the bridge swaying more and more till it collapses. Have you seen video of guys getting pitched from seriously violent tank slappers while doing top speed salt flat runs? As soon as they get pitched, you see the bike ride off in a perfectly straight line sans rider, like some bucking bronco finally relieved of its unwanted cargo. No rider grabbing the bars, no tank slapping.
Anyway, I don’t think anything is really wrong with this guys bike, except possibly the stiffer springs idea (the springs are so ridiculously soft from the factory that this should be your first mod anyway, even if it turns out not to be contributing to the tank slapping). Every once in a while most any powerful bike under heavy acceleration will hit upon just the right combo of bump, rider grip, weight position, etc, to induce some tank slapping. If it happens a lot, you can try changing your geometry, get a damper, etc, but I don’t think a damper is really necessary for the SH (with mostly stock geometry).
Anyway, I don’t think anything is really wrong with this guys bike, except possibly the stiffer springs idea (the springs are so ridiculously soft from the factory that this should be your first mod anyway, even if it turns out not to be contributing to the tank slapping). Every once in a while most any powerful bike under heavy acceleration will hit upon just the right combo of bump, rider grip, weight position, etc, to induce some tank slapping. If it happens a lot, you can try changing your geometry, get a damper, etc, but I don’t think a damper is really necessary for the SH (with mostly stock geometry).
Senior Member
Back Marker
Joined: Dec 2004
Posts: 147
From: Los Angeles, California, Canyons = SMM's, ACH,
Worn, misadjusted steering head bearings can contribute to a head shake problem and the shawks stock ones are ball type and weak.
Also, when you replace them with aftermarket tapered ones you have to 'preload' the bearings.
The tapered bearing preload gives you some damping effect and I haven't had much problem with head shake since going to 'tapered steering head bearings' .
May as well put those in, your going to need them soon if you brake really hard, updated your brakes, or like to do a lot of wheelies.
~Jeffers
Also, when you replace them with aftermarket tapered ones you have to 'preload' the bearings.
The tapered bearing preload gives you some damping effect and I haven't had much problem with head shake since going to 'tapered steering head bearings' .
May as well put those in, your going to need them soon if you brake really hard, updated your brakes, or like to do a lot of wheelies.
~Jeffers
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Posts: n/a
I had never experienced anything other than mild head shake. But I live at 6000 ft. and was down on power and replaced the shock and reworked the forks right away.
At the track I got pretty bad head shake with the reworked stock fork on a particular corner over a rise and dropoff at the track. No problem after a steering damper.
I genereally think of a tankslapper as the rear of the bike pivoting about the steering head. Yours sounds like what is referred to as headshake.
Good to hear it is a known problem and not a bent motorcycle.
At the track I got pretty bad head shake with the reworked stock fork on a particular corner over a rise and dropoff at the track. No problem after a steering damper.
I genereally think of a tankslapper as the rear of the bike pivoting about the steering head. Yours sounds like what is referred to as headshake.
Good to hear it is a known problem and not a bent motorcycle.
Member
Squid
Joined: Mar 2005
Posts: 62
Hi,
I didnt get progressive springs, just a firmer spring rate, and the difference this made to the bikes handling is amazing... as the others said, you should do this regardless.
I also added a 6mm spacer at the rear and dropped the forks 5mm which has steepened the steering angle considerably, and other than (what id call) gentle headshakes i have not had a tank slapper since.
I didnt get progressive springs, just a firmer spring rate, and the difference this made to the bikes handling is amazing... as the others said, you should do this regardless.
I also added a 6mm spacer at the rear and dropped the forks 5mm which has steepened the steering angle considerably, and other than (what id call) gentle headshakes i have not had a tank slapper since.
Senior Member
Superstock
Joined: Jun 2005
Posts: 406
From: Trussville, Alabama
Re: steering
My guesses (if the problem is repeatable / persists)
Suspension setup and/or front tire.
Just curious, you mentioned it occured just as you got to redline.
Did the oscillation start while you were still holding the throttle open, or did it start right when you rolled out of the throttle (to slow down or shift gears) ?
Suspension setup and/or front tire.
Just curious, you mentioned it occured just as you got to redline.
Did the oscillation start while you were still holding the throttle open, or did it start right when you rolled out of the throttle (to slow down or shift gears) ?
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