Front end vibration...

[BUSA_CHeMiST]

Ok, so i've been dealing with this front end vibration for a few months now, and nothing I seem to do to it is fixing the problem.

The vibration is a side-to-side wobble (like a tankslapper) between 40-55 mph and anything +110mph.
Example: Say i accelerate up thru that range, get to about 70mph, and let off the throttle and completely let go of the handlebars...as the bike deccelerates thru that range, 55-40mph, this "tanklsapper" vibration occurs.

Now, for the list of things we have checked and changed..

-Front wheel balanced? Yes
-Tried 3 different front tires now.
-Changed fork oil, fork seals, washers.
-Changed wheel bearings/seals
-Changed steering head bearings, but did not change out the races.
*when I pulled the head bearings and checked the races, everything looked brand new! So
I dont believe this is the problem.

So, does anyone have any ideas? I have a track day TOMORROW and I really didnt want to have to live with this vibration. I mean, its bearable, but scares the livin $h1T outta me if im leaned in a turn and i might be close to that range.

HELP, AGAIN!

Chemist...

 

[300Busa]

have you tried putting the bike on a front stand and spinning the wheel to see if it spins straight?

 

[BUSA_CHeMiST]

Yeah 300, everything seems true on the front wheel as well.

Wheel seems to spin fine as well, besides the usual drag from the pads

 

[300Busa]

just a thought, but maybe the problem actually exist in the rear? Do the lines match up on the swingarm for the rear tire alignment? Sounds like you checked everything else it could be...

 

[BigDawgZ28]

I had a similar problem..It turned out my rim was bent..Id get a nasty headshake at around 55 mph

 

[300Busa]

I had a similar problem..It turned out my rim was bent..Id get a nasty headshake at around 55 mph

that was my first suggestion, but he says that it isn't. It may be too slight of a bend to see with the eye.

 

[HillbillyTom]

just a thought, but maybe the problem actually exist in the rear?  Do the lines match up on the swingarm for the rear tire alignment?  Sounds like you checked everything else it could be...

On my last bike, after putting on a set of Corsa 3s, it started a steady oscilation of the bars over 90 mph, mild headshake. "Riding the fish" I called it. Not bad and never got worse so I lived with it, rear tire wore out and I replaced it with a half worn PP I had to finish off the front, and suddenly, no more "riding the fish". Yes, check everything on the rear wheel too.

 

[Scar]

I'm inclined to look to the rear, as well. If everything in the front checks true, then I'd start looking elsewhere.

I'm no expert grease monkey knuckle-dragger, but it sounds like you've exhausted the possibilities at the front. So... Bent rear rim? Bad rear tire? (have you changed the rear tire, as well?) Swingarm solid? Engine mounts?

Grabbin' at straws here...

 

[pbghost]

didn't see it on the list...any chance a slightly warped rotor would cause this? is anyone close by to swap out front wheels for a test run with you to see if it cures the problem?

 

[BUSA_CHeMiST]

FOrgot to mention when the problem started...

Took the bike in to get a new front put on. At that time (back i early march) I didnt have a front wheel tool so I let the guys at the shop take it off and put it back on. Left the shop on a Shinko 009 Raven. Hated the feel, very slick, people here told me it would take forever to scrub in, so i took it back the VERY NEXT DAY (no vibration at this point). Next day, another tech works on it, pulls of front wheel, wraps it in a brand new Dunlop Qualifier, reinstalls front, and im off again. Tire feels 100% better than the Shinko but the VERY FIRST light i pulled up to, I noticed that vibration as i let off the throttle and it decel'd thru that speed range.

BTW, everything is lined up on the adjusters on rear wheel, chain is snug where i like it.

 

[BUSA_CHeMiST]

Scot, I have had an idea that it might be a rotor, but both myself 2 mechanics up in Dallas have ridden it and you can't really feel the vibration as hard under braking.

We did put the rotors on a caliper to check, and they were somethin like 4/1000th's off being true, so i cant say it is that.

 

[Scar]

FOrgot to mention when the problem started...

Took the bike in to get a new front put on.  At that time (back i early march) I didnt have a front wheel tool so I let the guys at the shop take it off and put it back on.  Left the shop on a Shinko 009 Raven.  Hated the feel, very slick, people here told me it would take forever to scrub in, so i took it back the VERY NEXT DAY (no vibration at this point).  Next day, another tech works on it, pulls of front wheel, wraps it in a brand new Dunlop Qualifier, reinstalls front, and im off again.  Tire feels 100% better than the Shinko but the VERY FIRST light i pulled up to, I noticed that vibration as i let off the throttle and it decel'd thru that speed range.

BTW, everything is lined up on the adjusters on rear wheel, chain is snug where i like it.

Is your bike lowered, Chemist? Based on the pic in your signature, it looks it.

 

[BUSA_CHeMiST]

It was lowered Scar, had 3-hole dogbones on the rear. Those have since been swapped out for stock bones so its back up to stock height now.

 

[MPH 200]

Jerry have you changed the oil in the stock damper, this won't solve the problem, but it may cover you for tomorrow?

 

[Scar]

It was lowered Scar, had 3-hole dogbones on the rear.  Those have since been swapped out for stock bones so its back up to stock height now.

...and you're having this problem since swapping back to stock, or did it occur while you had it lowered?

RSVP.

 

[BUSA_CHeMiST]

Mike, oil HAS been changed in the stock damper. 2x now. Both times I went with a 75w oil. The problem started about a month after changing the oil the first time. (2nd time i changed it was yesterday just to make sure i hadnt left any air in it)

SCAR, the problem began while the bike was still lowered.

 

[Scar]

SCAR,  the problem began while the bike was still lowered.

So, hm...

is the vibration any more or less pronounced lowered or not? Or is it status quo?

 

[BUSA_CHeMiST]

same intensity both lowered and stock.

 

[Scar]

same intensity both lowered and stock.

K. I'm going to call a local dealership mechanic...see what he thinks.

I feel your frustration.

 

[mike1180]

I think it is from the rear also.
Bad tire, rear bearings, bent rear wheel could do these symptoms also.
Have you got anyone with a Busa that would let you swap the front wheel to test?
That would be the only way to totally eliminate the front wheel causing it.
Fastest way to move forward.
If it is still there, then swap out the rear and see??

Mike A