Posted: 7/13/2008 2:11:40 PM EDT
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www.youtube.com/watch?v=xUBwCX_Mv2Q anyone ever had this happen? i have once..got lucky and saved it. |
I don't enjoy seeing people get hurt,  and I think that it is in poor taste for someone to set it to music and post it on the internet as entertainment.  I realize that you are not the person who did that, Zack. 
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Exactly. It's normal for the bars to wag when you're not completely straight up and down and the front end gets light under acceleration. But it's a high-frequency low-aplitude motion, and it doesn't hurt anything. The area where people tend to get into trouble, is by mistakenly thinking that the handlebars are an attachment point for the rider, and/or by responding to the wagging bars in the wrong way- shutting the throttle and/or applying the brakes shifts more weight onto the front wheel, steepening the rake and reducing the trail. Trying to hold onto the bars simply adds a portion of the rider's mass to the oscillation, reducing it's frequency but INCREASING it's amplitude. When you're on the gas, you should only be holding onto the right bar, and even then, only with your thumb and one finger. It takes very little steering motion to turn a motorcycle once you're above a walking pace, so a lot of racers apply sticky-back lead wheel weights to the steering stops to reduce the amount of steering travel available, to limit the absolute amplitude potential of wagging bars. |
there are several cures..but i agree that cranking the throttle is a good one. that's what i used to cure mine. releasing the handlebars can also help, as well as just shifting your grip on them a bit. the mechanics of a tank slapper are somewhat complex, but the basic idea is that the front tire accelerates laterally for one reason or another, and then recoils back. if the conditions are right (or wrong, depending on your point of view) this action will continue, oscillating stronger and stronger until the bars are hitting the end of their travel at each end, resulting in what's known as a death wobble, speed wobble, tank slapper or what have you. to cure it, you've got to stop that oscillating, or you go splat. if you are quick enough and crank the throttle, you can get that front wheel up before you get in too much trouble. if not, you've got to adjust the ...frequency at which the steering assembly, and to a certain extent the entire bike oscillates by other means. Sometimes simply adjusting your grip on the handlebars will do the trick. you also might just let go, as a previous poster in this thread suggested. more often than not, tank slappers do result in a crash though. best to try and avoid them. that goes without saying though.  ...or you can do this: www.youtube.com/watch?v=PU0VstC82Fg (i do not advise anyone to try this)
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Who is that guy? I see that video all the time. |
like I said I hit the rears and got the slap out. now go back to your hole kirk. |
Valentino Rossi back in his 125 days. -p. |
That's not a 125. |
yep I need a dampner too I just roll off the throttle slowly as i tried cracking it open when it happened it just seemed to stay the same or get worse let of the throttle in a non abrupt manner and it quit never had a big one though |
I have not had a good wobble out of the my FZ1 for quite awhile finally can enjoy the thing some without thinking Im gonna die now hey I never owned anything bigger than a 600 4cly or 800 twin before |
So what is different now- I think we talked about this before, but I forgot. Was it a tire change that fixed it, or did you ease up on the bars, or what? |
Okay. What is it? Rossi has run the number 46 on every other bike. That's definitely a two-stroke though the tires don't look skinny enough to be a 125. Maybe it's someone wearing a Rossi helmet? -p. |
The video's awful fuzzy, but it looks like the number "1", not the number "46". I'm guessing it's old, because they are using hay bales on the side of the track. I see two silencers on the right side of the bike, so I'm guessing it's a 250 2-stroke. The swingarm is not single-sided, and the bike has an aluminum perimiter frame. I also observe that the tail section is pointy. I'm having trouble finding decent accurate pics of old Honda 2-strokes, but I suspect that it MAY (and this is only a little more than a guess) be an RS250, or an NSR250R from the '90s. |
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Mine happend coming over a hill while in a slight left bank and on the throttle the front end got light and started to wobble slightly then started getting worse, cranked the throttle...smoothed it right out...rode home changed my shorts. To the guy that said he used the rear brake to smooth a wobble...you got very very lucky my friend. Glad you made it out OK though. |
+1 Harley just settled another case out of court as their FL line has had this problem for years at speeds over 80mph. Conditions have to be just right, but too many have had it happen. In Harleys case it is a function of rubber swing arm/engine mounts and front end geometry (the frame neck is in front of the forks and less rake on these models). The cure has been stiffer poly bushings, a brace and a bigger OD rear axle. My RoadKing doesn't seem to be affected, but I am religious about wheel to wheel maintenance (too many old Harleys in the past). |
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en.wikipedia.org/wiki/Speed_wobble Usually happens when the front wheel comes off the ground and then comes back down out of alignment with the back wheel. Can be from a wheelie or rough road while accelerating hard. I'm sure there are other causes but these are probably the most common. |
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I had it happen! Scared the BEEJEESUS out of me!!  Honda CBX..........sometime in the late 1970's. It was stock except for six Denco pipes like this:  It was fast and sounded like a Formula 1 car!!! But the frame was made out of rubber...........and it got into a tank slapper on the off ramp of I-4 in Orlando with a pretty girl on the back right behind me!!!!! I had to grab a handful of throttle to settle it down.......  No.....I didn't say anyhting to the girl but my knees shook for two days!!!  |
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Smirking at the above poster. I too can claim to have suffered a "tank slapper" on a CBX1000  Just over a ton on the motorway when a (big) gust of wind hit me. I just froze...did not brake did not accelerate...just froze.  And it went away. Fucking scary Only time this happened before was thrashing a suzuki GT750. That was just as scarey. Cheers Taffy ETA I do have pics somewhere of the offending bike. I'll try to scan and post them |
mostly getting comfortable with the power and am not white knuckling the handlebars any more got the tires to a proper PSI for me anyway and had a tech buddy of mine soften up the suspesion a little |