Who's had BAD tankslappers at the track?

[JSpin]

so yesterday was the first time in quite while where i've been really scared on a motor cycle. it happened right after i crossed the finish line. right as i shifted into high gear and got out of the throttle (never touched the brake), the bike went into the worse tankslapper i've ever experienced. it lasted FOREVER, all the way past the first return road and maybe to the second, not sure. it was long enough to really have time to think about what was going on, i thought for sure i was going down. the bike finally came out of it, i guess after it slowed down enough for the dampener to get ahold of it.

i've really never done much with the bike chassis wise, just did what i could with the stock parts. still have the stock front end and dampener w/ a strap. i also recently added a new front wheel and a small tire. i can't really blame it on any one thing, just a combination of everything. it's time to have my forks done and invest in a good dampener. i'm also going to good hard look at the front to make sure everything is strait.

does anyone have any opinions on what may have happened? i've always been good about rolling out of the throttle and letting the bike roll for a while before sitting up and getting on the brakes. but if there's something i may have done to contribute to what happened, i'd like to hear it.

[2ten Hu$tla]

about 4 months ago i had got one at little river that was violent around 1000ft when i came back to the pits my father was looking at the front tire and you could tell i had ran over something like a bolt and im thinkin that might have been what happened to you if you were testing and tuning and cars were out that may have been the case because cars lose alot of junk on the track that the track crews dont always see when they clean up after them just my 2 cents

[KATRACER]

A few years ago I went across the finish line with the bars slapping pretty good. To me it seemed like a bit of a 'wild ride', I was maybe a bit concerned but nothing serious. The top end crew stopped me on the return road, and the girl there had tears in her eyes and asked me to please not ride that bike again. Scared the **** out of her. The other top end guy said I should probably park that thing too! I thought to myself it must have looked way worse than it felt? When I got back to the pits, my mom and dad both said I "better park that bike".
The biggest thing I think was the front end of my bike. Original stock-skinny-soft front forks. No dampener either. A better more modern front end or even this front end properly set up would have been better. The bike was an '81 GS1100E.

Low front tire pressure, soft forks (bagged springs, low fork oil), strapped too low, loose steering head bearings, there's a few things that can contribute to 'tank slappers'.

[Goldenchild]

Check balance of tire,Phil had the same issue come to find out tire was bad

[JSpin]

thanks for the responses guys.......i'm definitely going to have the front wheel and tire checked out as thats really the only recent major change i've done suspension wise.

[TURBO STEVE]

check the tire for sure, and what kind did you put on? i had it happen to me and to find out the little pirelli tire everone is buying was bad on mine, i put the rim and tire on a balancer and omg it was lumpy, wobbley u name it, i took the tire off put it rite in the garbage and put a different tire on it and that was the problem, but check EVERYTHING in the front end and yes lose the strap, if you straped and the tire is bad...... hold on!!

[07busa]

yea and get a better stabalizer the stock ones are garbage

[zooki01busa]

Yea, I had one at around 160mph (not at track) on a highway.Racing a guy and while passing him noticed he was kinda waving me off.My dumb azz kept the throttle to the stop only to find out a railroad track crossed the highway just ahead,I went over it at 160ish and it started shakin big time !!! I hung in there and road it out but had witness marks in my undies....LOL... Have heard that bad steering head bearings can make you shake up front tho....'cheers;

[N/T 919]

Check balance of tire,Phil had the same issue come to find out tire was bad

i had the same problem cycle gear (never again) put to much weight on the rim & not enough psi in the tire make sure you have 42psi.

[kawasakijockey]

A rake angle under 23.5 degrees can lead to a tankslapper. Sliding the forks up the tree, strapping the front, and a smaller front tire will all contribute to decreasing the fork degree number. When you let off the gas or touch the brake the weight loads toward the fork and worsens the angle more. Once you hit a bump things go out of phase and there starts a tankslapper in a lot of cases.
A bad tire could be the problem as already stated. The wrong type of tire was the number 1 problem on our old KZ's and GS's. I ran ribbed front tires that never gave the problem on my old bikes. Like already stated, check your headtube bearings too.

[Jetlag]

Check your forks and see if one or the other is uneven in the clamps or if one is leaking oil and the other is not. I have used the stock stabilizers and replaced the oil with motor oil to stiffen the stabilizer. Works great and saves money!

[Bobby Busa]

I agree with it being a tire issue. Either a bad front or out of balance. I used to be one of those guys that didnt worry with balancing motorcycle tires because I didnt want those weights to make my rim look ugly. I found out the hard way one day while out for a ride that that was a stupid idea. I got in a terrible tank slapper that I didnt think I would get out of. I did get out of it thank God. Turns out my front tire needed balancing bad. Now I always balance the front and dont worry with the rear. I hope nothing goes wrong with that!

[Hybrid]

I have used the stock stabilizers and replaced the oil with motor oil to stiffen the stabilizer. Works great and saves money!

Yes the stock oil in those dampers are crap! I put 20W fork oil in the damper and problem solved, no more tank slappers!

[dave393]

If you are using adjustable lowering links, they must be measured eye to eye with a caliper before installed. I have seen wobbles because of this set wrong.

[motorbikeboy39576]

I RODE A 04 R6 AND HAD A TANK SLAPPER AT TRACK ALMOST HIT GAURD RAIL WHEN I GOT TO MY HOMEBOY WHO THE BIKE WAS FOR MY LEGS WOULDNT STOP SHAKING FOR A LONG TIME.I WENT DOWN CROSSING A BRIDGE I WAS ON A OLD KZ550 THAT ALMOST TOOK MY LIFE .