fork twisting slapper!

[RedexRobB]

My god the front end of my bike lately is giving me no end of toad, lately! :smt013

Yesterday on the way back from work i managed to have what id call the most severe tank slapper ive ever had. Theres a bump in the road where they have resurfaced it, but its one of those bumps where they have over filled it to allow for compression of the tarmac, except there hasnt been any and is now a 'pretty viscious throws you butt out of the seat bump'.

I hit this bump everytime i come back from work, it goes right across the carriageway and theres no avoiding it. Except yesterday i had to change lanes as i was approaching it. Result, wibble fucking wobble i tell you thats what!! Bars turning to change lanes and hitting that bump were never going to be a good combination. After a good couple of whacks from steering stop to steering stop, and thumbs getting a good squashing, I managed to retain my composure and ride on, but got a mile down the road and realised the bars didnt feel right. Took a look at the top yoke while riding in a straight line and the ignition barrel definately isnt point as far forward as what it was. f*** they are twisted, took a look this morning and got the top yoke as straight with the H frame as i could, took a look at the wheel and its definately pointing slightly to the right.

Anyone else ever had this? Look like im gonna have to loosen it all of today and see if i can straighten it out Any tips? On how i can do this?

[wonderpupp]

If the forks weren't clamped in properly to the Yokes, this can happen.

Had a similar event with my kmx200, it was just the forks rotating in the yoke clamps. Was pretty easy to straighten out, just loosen the clampy bits and straighten up and tighten up really good.

Have you ever ridden a bike that when it rains, it runs in reverse? That was scary RD125DX...

[RedexRobB]

running in reverse?

I think the clamps were done up tight enough, it was just so violent that the wheel generated enough inertia to twist the forks. Like i say there was a good couple of whacks against the stops too. When i pulled off about a mile later i had no brakes either; it rattled the pads back into the calipers.

Gonna straighten them out in a minute actually now that ive got a bit of time.........

[cargo]

Just what do you mean by "tightenup really good"

Let me put it another way if you tighten the fork clamp bolts beyond the correct torque setting the bolt will stretch....................................it will be weakened and could snap.....................be more than your forks twisted if that happens.

[jake]

they dont need to be very tight either, ive seen damaged forks resulting from this!...erm..not mine tho
if ever an excuse was needed for that lovely tourqe wrench, then forks clamp bolt are it

[RedexRobB]

Well i think ive done it. Will see how it feels in the morning, but a piece of wood wedged between the screen brace and fork tops kept the forks pointing straight, and a longer bit pushed up against the rear wheel extending to the front wheel gave me a way to measure the distance at the front and back of the front wheel.

While undoing the clamps they didnt take much effort, may be due to when i set the forks back to standard ride height but either way, they have been fine for quite a while like that which proves the point they dont need to be that tight. On that note, my friend had a motorcross bike, and his dad used to loosen off the fork clamps so there was some 'give' which, saved the forks getting bent when we inevitably dropped it.

[Jamz]

From your OP I was going to say it would be pretty unusual for that to happen without it pushing the pistons back in as well!

It must have been a bloody violent one, though!

I've had probably 30+ tankslappers today around Oulton Park, so you'll get no sympathy from me, though!

[RedexRobB]

Volent it was. Ive had a really fucking painful neck ache since tuesday, and i thought id pulled it at work. But the gf said to me yesterday maybe it was that incident id had the other day on monday and it all became very clear, so maybe a mild case of whiplash?? Went to the doctors last night and has prescribed some pain killers, but my god it hurts Anyone else ever had a sore neck after a slap up?

[SOILZX]

I had a real nasty 1 on the 636 at the end of last year coming back from Angelsey. Basically riding like a complete TWAT, trying to get home before it got dark (come to think of it, it was the same road i smashed the thing up on), went round a sweeping right hander, flat out in 3rd went for 4th and just went into a horendous slapper, bearing in mind i was doing well over a ton! It was just pure luck that i didn't crash, no skill involved what so ever!! I have to say, thats is the 1 only and time i REALY prayed!! The next day i was sore as hell round my neck and shoulders. After that, i wasn't quite so scared of tank slappers, they turned out to be a regular occurance on that bike, they realy do need a damper.

[Jamz]

I had a real nasty 1 on the 636 at the end of last year coming back from Angelsey. Basically riding like a complete TWAT, trying to get home before it got dark (come to think of it, it was the same road i smashed the thing up on), went round a sweeping right hander, flat out in 3rd went for 4th and just went into a horendous slapper, bearing in mind i was doing well over a ton! It was just pure luck that i didn't crash, no skill involved what so ever!! I have to say, thats is the 1 only and time i REALY prayed!! The next day i was sore as hell round my neck and shoulders. After that, i wasn't quite so scared of tank slappers, they turned out to be a regular occurance on that bike, they realy do need a damper.

Glad it's not just me! Then again the R6's I've hired were almost as bad for it... I was speaking to some people the other day and now I'm pretty sure having a quick-shifter would cut the slappers down a fair bit, because a lot of the ones I was getting on track were certainly being helped along by snapping the throttle shut and open between shifts - of course with a quick-shifter you won't be putting the extra input into the bars because you can keep it pinned...

To be honest the ones I've had on the road I can't really remember whether I've been shifting up. Definitely possible, though.

As for the body mechanics of it all, from a martial arts point of view wrenching someones arms when they're at that angle (sportsbike riding position) I'd expect the damage to be between the shoulderblades and high up?

[RedexRobB]

The next day i was sore as hell round my neck and shoulders.

Pretty pleased to hear that from the point of view that i now know that it was more than likely the slapper and not something i did at work! Im not hat sadistic that im pleased to hear you were sore!

went over 'that' bump today, feeling rather alert and ready for a another slap up as i approached, but today, no drama