Front End Vibration Issue

[LA Busa]

Ok, after a few hits maybe the mods can move this to the Maintenance section, thought I'd get more initial hits here...

'06 Busa, 14,000 miles, Spiegler lines, stock pads (after having used EBC HHs for a while), MANY (probably 8 or 10) track days, no wheelies or stunting, B'stone 003RSs - I never let them get old.

Bike has had a vibration up front under braking for a quite a while, under braking is the only time anything shimmies. Replaced the rotors with used set sometime ago, better, but still there. 3 sets of rotors later I began to suspect that maybe, its not the rotors. Saturday AM I rode and went from... a high rate of speed back down to legal velocity and the nose fairing vibrated like a Ducati at idle, scary.
I could just be paranoid, and I do ride other bikes that are WAY lighter, but the Busa's steering has felt 'heavier' lately. Like I have to really muscle the bars to make it feel right in a corner.

Propped the bike up last night with the front end off the ground, sat in front of the front tire and noticed a slight front to back bit of play. The suspension would sort of knock as it hit the to a fro stopping points. Aha! Moved around to the side and put my left hand on the front of the front tire and my right hand on the left bar end and pulled and pushed, play there too.

Dropped the Busa down and did the same thing with the 1098 and the ZX6, no such similar play in either of those, newer, similarly used bikes.

Called an expert, said its the steering head. YES, I HIT THE SEARCH BUTTON HERE, found some useful data.

This AM, I ripped it apart down to the forks and triples with the help of my lovely and talented assistant!
The play I was feeling is in the fork tubes, not the head. I pulled / pushed and twisted the triples and got nothing but smooth, easy movement.
Each fork tube has a bit of play between the lower and upper portions. I would say they each moved about 1/8" or so and knock as they are pushed back and forth (not in and out). Essentially, they have play in the same direction braking forces would be applied.

I dont have another Busa to compare against (will this week) but what I am asking is do Hayabusa forks have any designed play between the lower and upper fork sections? Again, the 1098 and ZX6 do not have this play, I checked.

Thanks in advance for any thoughts!

 

[smac]

See if Ben will bring his bike over and let you check it, I will be happy to let you check mine but it's a gen II.. Good luck..

 

[LA Busa]

Ben WILL be by for a comparo! He is hanging out among tanned beauties on the beach this weekend or I'd have had his bike over here this AM!

I am pretty close to flummoxed and need to compare the play in his to mine before going to plan 'B'....

 

[HillbillyTom]

No, there is no play in the fork tubes. Play in the tubes is called "worn fork bushings".
Is strange that they are worn that much, with that few miles. And you've had no fork seal leakage problems?

 

[LA Busa]

I replaced the fork seals about 6 months ago, they were leaking.

Why am I not finding fork seal bushings referenced in my shop manual? Does the lower tube just 'ride' in the ID of the upper tube or are there replaceable bushings in there?

 

[delbert]

i enquired about this some time ago , apparently the bush is part and parcel of the lower leg

 

[HillbillyTom]

I'd never looked into it before, but after searching some parts fiches, there appears to be no replaceable fork bushing in Busa forks.
Esh, that could be expensive. I've never heard of a street bike doing this, only dirt bikes with 12+" of fork travel (they have replaceable bushings, where I came up with that at).
Dunno. Hopefully someone else will come along with some more info.
Bump back to the top..

 

[LA Busa]

The lower 'leg' is just a smooth tube.

I think your right Tom, no replaceable bushings on the fiche that I looked at either.

Weird. I'll do a comparo with another similar Busa this week and post up.

My thinking is that there might be some 'built in' lash in the tubes, I have not been THAT hard on Mr. Busa.....

 

[DEMMYM]

What conditoon is your front tire in, I had the same problem, Swapped front tires and now no problem

 

[LA Busa]

Tires are good, this has happened over about a year and with several sets of tires, on the track and on the road...

One board member has offered me some spare fork uppers in case I need them. Still some research to do...

I see my wife the MODERATOR relegated this post to the hinterlands.... Maybe someone will see it anyway - heck, I could not even find it

 

[Professor]

There is a bushing there in the lower end of the outer tube. It is not a service part from Zuk, so it does not show up in the part guide. The service manual says to replace the tube. It may still be something that is available from KYB or aftermarket.

 

[Professor]

Bump!

What did you figure out?

 

[dmallord]

i have read that you are leaning towards possible fork tubes...

but, i would be very curious as to how much lateral runout (dial indicator, refer to spec)
your rotors have. once you load the fork tubes, as in braking, i would think that the play would be taken up in that direction. brake load causing the tubes to push back to the rear limit of the play.

3 sets of rotors. was the problem solved only to recur? if so after how many miles/ track days? if you are generating extreme heat you will keep warping rotors.


not for nothing, but if the rotors have excessive runout that will translate right up to the bars.

 

[proelky]

I had an similar issue when I anodized a set of ZX10 forks. The plastic bushing is not serviceable from the factory, and is only available when purchasing the lower tube assembly ($$$$). I don't recall the company, but they offer the bushings for $15 a side.