Tank Slapper anyone?

No flame PB, just an option...

2.a) opional - if you have no friends, or no heavy friends, one can place a jack under the exhaust to lift the front wheel.

This option ensures the maximum amount of cold beverages :tea: for after the check ride that would otherwise be provided to the friend(s). since the friends do not have an opportunity for unsupervised beverage consumption while the check ride is occuring. don't ask me how I know this.

:wink:

 

I had this happen when I was riding up north. When was the last place you got air in your tires from? I topped off and it turns out the compressor had enough water in it that it filled the tire with enough water to shake me to the point that I swore I would never buy another Dunlop. Simple remedy if this is it.hope this helps ya out.

 

I'll try and make this short...
I totaled my first VFR(2002) 2 weeks ago. I'm OK(miraculously), but very sad to have lost such a great ride.

New set of Dunlop Qualifiers <1500mi on them.
I'm meticulous about tire pressure, and check at least once a week.

Riding the twisties. started to pass a car, dialed up speed, and gave aggressive input to the steering to get back in line in front of the car. Somewhere between/during completing the pass & braking for an upcoming turn the front end started wobbling uncontrollably. I lost it and high-sided.

I don't remember details, only that the head shake was uncontrollable, and I had never experienced it before coming from a cruiser background.

Relevancy: It seems to me that a steering damper is essential for any performance motorcycle with a relatively aggressive rake angle.
Why doesn't the VFR come with one from Honda?
Do you think an after-market(e.g. SCOTTS) damper is a wise investment?

Thanks for the input.

BTW a new VFR is on the Christmas list!

 

I just posted about this recently on my 99 with high mileage and a bad front tire. The other day I lightly let go of the bars and rear braked a little, the bike started wobbling something fierce.

Now I noticed mine has a definite catch dead center in the steering. Probably time to get the bearings changed out, along with the tire.

 

With the VFR's stock rake and trail a steering damper in unnecessary IMHO. Had you raised the forks in the triple clamps?

If you just had a tank slapper/high side/total loss, I would think it would be a wise investment for your peace of mind. I know the Scott's is available for the VFR.

 

Is this a modification? Any former threads about this?

I had bought the bike from a one owner with ~6700mi. He didn't mention any mod, and there wasn't any visible difference in the triple tree compared to showroom VFRs.

I think you're right about my piece of mind. On the other hand, IMHO, when a bike is pushed to the outside of it's perfectly engineered Honda limits, it could benefit from steering damping.

However, steering damper or not, my goal now is to figure out what causes wobble (on a perfectly maintained bike) and what to do about it when it happens. i.e. NOT crash :frown:

Thanks for the reply.

 

A very popular modification is to raise the fork tubes in the clamps a few mms. It makes the bike easier to turn, at the expense of stability by increasing rake and decreasing trail. If you go too far with it you can experience problems with wobble and/or a tank slapper.

I am assuming what you experienced was a tank slapper, correct? I don't think there is much if anything you can do once the bars get away from you, just slow down and hope that it corrects itself before you crash.

 

Actually, slowing down will make it worse by putting more load on the forks. You want less load - not more.

Lean back and accelerate. This will reduce the load on the forks and allow them to re-establish equilibrium.

 

I agree. From what I've seen, this seems to be the best thing to do. If you have room, dial up a handful of throttle to unload the front-end. The situation I'm concerned about is not when you have room to accelerate, but when you're facing a tight corner or other obstacle...Then what?

It also seems intuitive to me that loosening your grip and letting the bike settle itself is a good remedy, unfortunately this goes against our nature of wanting to hold on tighter. I believe we're not fast enough to correct the oscillating bars and only end up compounding the magnitude of the wobble by trying to control it. I've heard the Chuck Yeager generation of test pilots had a name for this method: the J.C.(Jesus Christ) maneuver. Just let go and let God. :smile:

 

I have a question or two for the knowledgeable Gen 6 members. I am only 66kg or 145lbs. I found the suspension very firm compared with my VFR750 Gen 3 so I set about trying to rectify the harsh ride by fiddling with something I know very little about. I’m a bloke that’s what we do, isn’t it?

I just purchased the 02 a while back and the forks were raised 10mm or 3/8" from the ring to the top of the clamp, I suspect this is not standard.



My question. What would the standard height be? Could it be the ring level with the clamp or a gap of?

The front pre load was screwed down level with the top of the forks (i suspect because the forks were lower than they are normally?). I backed this out till I could see two rings on the preload adjuster but the bike seems to oversteer almost to excess now.
I removed all preload from the rear shock and set the rebound to the centre, about 1.25 turns from full hard. This helped with the ride.

After reading this post I am a little worried I might end up on the tar from a big unexpected wobble, I’m a little too old for that type of caper now.

My old Gen 3 was a bit tough to turn so I dropped the forks about 7mm ¼” from standard and I like the way it handles. It now oversteers a little but is not unstable, sweet.

Thanks,
Bluey

 

Concerning the J.C. Maneuver...

Holding the bars loosely does have its advantages. My friend has a masters in thermal fluid dynamics and he discovered an interesting thing while riding his V-max at - shall we say - above the speed limit ;-).

If he gripped the bars, the bike would do a little wobble dance. As soon as he loosened his grip or let go, it would stop.

He explained it to me this way. When wind or water goes past an immovable non-streamlined object, it creates eddies on each side of the object. First one side, then the other.

This is what the wind was doing as it was going past his body (250 lbs) - creating an oscillation. The wind was moving his body - which was moving the bars of the bike.

If you follow a semi-trailer at just the right distance, you can feel it as the wind beats you up from first the left, then the right.

 

Well I went to the local dealer today and had a look at the forks on the new VFR 800. They had 2 new bikes a Red and a RWB. Both bikes had the front forks lowered about 5mm to 6mm from the ring. Mine have been lowered twice that amount .

I ran the bike up to 95 kph and let go of the grips and it did the big very fast wobble It won't do it unless you let go of the steering. I have a Battlax 014 with only 1 mm to the wear indicators on the front, I suspect this could contribute to the wobble. When I got home I screwed the pre load adjusters back down flush 5 turns, should fix this small problem.:smile:

 

first of all you just had a wobble..a tank slapper will scare the crap outa you IF you survive it..I have only had 3 real ones in my lifetime, first where i ended up letting go the bars as couldnt hold them, and it floopped instantly, big mistake that. reason why they have dampers on the bikes now...luckily i was slowed down and landed in the grass. The worst high speed ones I ever had were both on a 05 vfr at 60 mph.a vfr!! not any of my other bikes ever..go figure...It nearly ripped my arms off both times, I could hear the front tire squeeling as it whipped back and forth and when i went back i could see the rubber patern it laid down! , and it happened so fast i couldnt believe it! Only $% luck kept me upright..both times it was when i was sitting upright, just letting off the gas, and hitting a hole at the same , bad combo!!woweeee.....never do i want do that again..I held on as hard as I ever have and let it slow down.turned my arms to rubber almost but she quit! .a year later 2 miles from the first spot it did it again while I had one hand on the bars taking pics.....this time I just slammed on the rear brake to slow her down and it quit instantly......I never want to do that again! and wont ever sit up into the wind , slow down, and hit a bump at the same time..

As for the 40 mph no hands wobble. its quite common on a lot of bikes I have had over the years, lotsa factors cause it...easy fix, just hold on..

please dont do a tank slapper.

 

This shake was at 95klh or 59mph in the old scale, not 40mph. No it was not a slapper just a bit of a suprise.

My old vfr750 never behaved like this and I have the front down 5 or 6mm below standard. I thought with the rake on the VFR's they would always befave themselves.

 

It quite supprising how much difference dropping the forks a little through the triple clamps make, had mine at 8mm then tried 14mm for a few thoughsand K's and one Snowey run, found while I loved its quickness through the tight stuff found the VFR was a little nervous at speed...

Raised it to 5mm a few months ago but find it dosn't turn in quite as quick as I like so will drop it again to 9mm to see if its just right.

 

John 451

John, What is the setting on your preload adjusters?
I heard you should see two rings from the top.

BTW the Ozvfr forum Registration Security code generator is still not working and I still have not been contacted:ballchain: I have tried a few more times to register but without the security code you cannot register.

 

You should work out your pre-load according to your weight and have a friend help with a long ruler, luckly I knew someone who knew how to for me.

For pre-load tips have a read of below link:
http://aprilia.rsvmille.home.comcast.net/~aprilia.rsvmille/bikes/suspension_guide.htm

Note - Have emailed you re OzVFR...

 

FWIW VFRs are touchy with their tires. Mine did the same thing till I went with Pirelli Corsa's Now I can no hands under a pretty decent deceleration with no head shake what so ever. I don't make a habit of doing no hands, but this phenomenon just bugged the H out of me.

 

My '06 Ninja 500R does the 45mph shimmy when I let go of the bars. The dealer checked steering head bearings, suspension, etc. and came to the conclusion that it was due to slight front tire cupping. It's not severe enough that I feel the need to replace my front tire. I have an older tire with plenty of tread sitting in the garage, but unless the problem gets worse I'll wait 'till the current tire wears out.

 

Thanks for all the great info. I'm guessing the tire is the problem, but since it is more of a deceleration wobble than a true tank slapper, I'll wait until I get a new tire before I go any further with diagnosis. A friend also suggested tightening the steering head nut as required by putting the bike on the center stand and getting the front wheel off the ground to feel for drag/slop as I turn left and right. No drag is bad - rough spots or too much drag is also bad. The bars shouldn't flop one way or the other, but should move smoothly with only very slight effort. Hopefully the bearing only needs tightened, not replaced. I'll let you know.