Tankslappers - how often?

[Quickly]

In the last six weeks I've had two violent tankslappers. The first time I was doing about 50 mph and it knocked one of the seat fairings off the bike. Last night I was doing about 75-80 mph and it knocked both seat fairings off and damaged the front fairing (to the extent that it eventually fell off). I've done probably about 2000-2500 miles in that time.

I know tankslappers can happen at any time, but I wondered if this sounds like a major problem with the bike, rider error or just bad luck. It's due in for a service in five weeks so if it's a small issue it could wait 'til then, otherwise I'll have to take it in immediately. The bike's a VFR400 by the way - they're supposed to 'ride themselves' they handle so well?
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[Paxovasa]

Tank slappers usually happen when the front end gets light.

Hitting a bump in the road, going over a rise in the road all while hard accelerating.

If possible get a steering damper fitted, that will help to stop tank slappers from happening.
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[Damon]

The vfr shouldn't really shake its head that much at all. I suppose some rough ground uner acceleration could cause one however.

[Wafer_Thin_Ham]

Never heard of them being particularly tank slapper prone on the road. Are you especially light and are all your bearings, tyres, suspension bits etc. in good order?
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[Nai]

Noob question time.... What is a tankslapper?

[Wafer_Thin_Ham]

[Blue_SV650S]

You really need to take a look at your head-race bearings!!

My NC30 had a few cheeky tank slappers, but never anything to get overly excited about ...
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[Paxovasa]

[Nai]

Ouch!

Couldnt help but notice this on the related videos... A tankslap recovery..

https://www.youtube.com/watch?v=6Fa0GmdSN4A&NR=1

Would be recoverin my brown pants if that happened to me

[Paxovasa]

[Spit-Fire]

in case you dont know what a high side is too
https://www.google.co.uk/search?hl=en&source=hp&q=high+side+wiki&meta=&btnG=Google+Search
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[Kickstart]

Hi

Bit of a wobble occasionally isn't that unusual and what some more excitable people claim as a tank slapper .

That it managed to be violent enough to dislodge the bodywork suggests a proper tank slapper (although not as violent as possible) which isn't normal. Check steering head bearings, wheel bearings, suspension damping, tyres, etc.

All the best

Keith
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[st3v3]

[Nai]

[GT Biker]

They generaly happen when the steering goes light (such as on hard acceleration) and you hit a bump or something. In my case I was overtaking and hit a crappy reflector caused a minor tank slapper. Seriously............a lousy crappy reflector in the middle of the road. Not exactly what I would normaly consider even a minor road hazard.
It only happened to me once and I was riding a slow and heavy b1250 lol!

[Ben.]

speed wobbles all the time under acceleration / wheelies, only ever had 1 tank slapper when i landed a good 20 -30 second wheelie (front wheel no longer spinning and probably put it down at an angle). That 1, I was at complete mercy of the bike.... i had no steering, i barely kept my hands on the handle bars... no way i could have opened the throttle, it actually pushed the pistons on my front calliper back in and I had to pump the lever to get my brakes back...
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[blutonium92]

I find the VFR to be one of the smoothest and most reliable handling bikes,

Iv had mine for 12 months done about 10k miles and only once had a tankslapper off it. That was when i gunned it up a really steep hill in first and hit a nice bump in the road.
But apart from that iv never had any head wobble or splappers.
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Had- 56 Aprilia RS50, 03 Aprilia RS50, Hond VFR 400 NC30, Aprilia RS250, Suzuki SV650

[Quickly]

Thanks for all the replies, I'll consider this all. The most suspicious thing is that neither happened under hard braking or accelerating. The first was as I was just leaning the bike up out of a corner, the second was on a fairly bumpy, dippy part of road (which would explain the front wheel picking up) but I was keeping the speed steady.
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[MarJay]

[cloric_tzr]

i had tank slap twice of my nc 24 both times i was accelerating very hard in 1st changed into 2nd agressivly whiles still picking the bike up out of a bend probably hit a bump causing major speed wobble. just power thru it. which is probably why it was major. scared the fu*kin crap out of me. i adopted a slightly less aggresive approach after that.
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[metalangel]

Have read a lot about these now, it seems:

-it happens when the front end is light, like hard acceleration or bumpy road
-front wheel might bounce every so slightly and then land out of alignment with the rear
-evil physics ensue as the gyroscopic effect of the bike trying to stabilize itself just keeps causing it to bounce from side to side.

And so you need to change something - either lighten or increase weight on the front end. Keep a grip of the bars but don't try and fight it. Conflicting reports suggest either accelerating or (rear) braking, though I suppose that depends on whether you have clear road in front of you or not. Squeeze the tank like (and I loved this quote) your girlfriend's younger sister. And the bike should straighten itself out if it hasn't chucked out off. In some cases, reportedly once the rider has gone flying the bike is immediately going straight on its own and drives merrily into a wall or sandtrap.

So, that's my ill-informed precis of what I've read.

The only thing that concerns me is the conflicting accelerate/brake advice. Does either work, is one preferable over the other?
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"A faired bike will get you 10x more clunge than a unfaired one." -Marlboro Matt

[MarJay]

[Kickstart]

Hi

My understanding is that the problem happens when the forks land up shaking at their natural resonant rate, hence they violently keep slapping from side to side (quite probably throwing the rider off and / or dislocating joints if they try and hang on). Most bikes will slap lock to lock occasionally when you hit a bump at an odd angle, but very rarely will this turn into a full on tank slapper.

All the best

Keith
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[swiftb]

Only ever had one tankslapper and it was almighty violent and pant staining. Happened after getting hard on the power out of a bend onto a very bumpy section of road. Unfortunately it happened just as I was along side a slower bike I was passing . Hit the lock stops on both sides a good 7/8 times, faster than you can shake a stick. My instinct was to hold on but in a relaxed fashion (not in any way try to stop it - I just sat there all limp hoping it would stop ) All this 'just gas through it' talk is all well and good but 99% of people will instantly do the opposite and shut the throttle.

[pepperami]

only ever had one tank-slapper in my riding life and it frightened me so much i was sick!

i came round a sweeping bend, accelerating very hard on my LC250
with all the trick bits.
i looked at the clocks and i was doing 85+ and rising (i must of been on a private road ), when i looked back at the road, i spotted that there was a half a house-brick sitting in the road .
not a chance to even think about it.... BLAM!.. left full lock....WHAM! right full lock, to left full lock, to right full lock .
the back wheel was about 3 feet in the air and all i could do was hang on and in those split seconds realise that i was heading towards the armaco barrier .

no skill was involved but the bike and me straightened out, i rolled off the throttle and pulled onto the hard shoulder.
feeling queasy i took my bash-hat off and had a good puke
it was then that i noticed that i had dented my tank with my thumbs on both sides (i had clip-ons) and it turned out later that i had broken both thumbs

i was quite pleased that my pants were still clean though
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