High speed vibration

[NemisusDM]

Hey Guy's
I went on a nice ride yesterday and I must say the old bike did quite well. The other bikes were :
07 Kawasaki 650R , 07 Kawasaki 500 and an 08 Yamaha R6. The XS11 lead the ride through the twisties.
The problem I had was above 100 mph. I get a wierd vibration and a loss of power . It feels like I'm rideing on nobby off-road tires. The speed is an estimate cause the guy's I rode with said they got up to 110 to try and keep up but, backed off.

[egsols]

said they got up to 110 to try and keep up but, backed off

Maybe keep it at 99 mph?

[prometheus578]

Hard to diagnose without being there....
Front tire tread might be cupping. Run the palm of your hand over the tread. If you feel raised areas from tread cleat to tread cleat... might be time for a new tire
As for the high speed loss of power and vibration... maybe you need to shift to fifth instead of winding it out in fourth gear all the time

[dbeardslee]

Nemisus - Here's some stuff that can cause a high speed wobble:

Tire out of balance or just a 'bad' front tire
Steering head nuts over-torqued
Worn steering head bearings
Warped front wheel
Tubes not properly aligned
Worn swing-arm bearings

I've got Chicken Skin Marquis and when I look straight down over the front tire I can see that the tread in the center is slightly raised above the rest of the tread. When that raised portion drops down in a groove on the road it wants to follow it like a slot car. It does fine on a nicely maintained blacktop road, but cracked concrete is a real bear. Next set of tires for this one are going to be Bridgestone Battlax BT45V's. I don't see how their tread pattern could degrade like the Chicken Skins have.

[olebiker]

These old girls don't have a very strong front end. If you are pushing it hard in the corners at high speed it will flex quite a bit. You might wanna brace on that front fork.

[NemisusDM]

Hey Guy's,
Thanks for all the quick replies...

Egsols, you might be right but, you have to have seen their faces

Prometheus578, Funny enough I can ride 4th all day long.....lol

Dbeardslee, good list....Worn steering head bearings would do that? feels like rideing on off-road tires even on smooth black top only at high speed though...if so then that might be my problem..I greased the bearings when I rebuilt the forks and they were bone dry and slightly glazed...

Olebiker, I don't have a brace on there yet but, I rebuilt the forks and it did get rid of the 70 mph death wobble and handles great in the twisties now.

[egsols]

you have to have seen their faces

I might not have seen theirs but I remember my buddy's. He was on an Aspencade, always called my 11 the "little bike", we were out on a ride, I pulled up along side and could see his speedo (digital) reading close to 100 mph, I smiled, he smiled back, he twisted his wrist, so did I, his smile was gone, mine wasn't.

Later he said, holy sh*t that thing has b@lls!

[dbeardslee]

Nemesis - What kind of tires are you running? An out of balance tire will resonate at different speeds, so you might not notice it all the time. Somebody told me once a long time ago that tires will resonate at about 30mph increments. You know, at about 30, 60, and 90 mph. He was talking about cars, but I think the same applies to bikes. I'd check the balance on the front tire before I did anything. It's easy enough to do. Mine was out of balance and it shook like crazy around 95mph.

[NemisusDM]

I have a Dunlop D404 in the front and a Dunlop K627 on the rear.

[dbeardslee]

Nemesis - I looked at the tread pattern on the 404's and it doesn't look like they would have the same groove following thing that you can get out of a ribbed design. I still say check the tire balance first. There's a bunch of threads that cover the process. There's also a thread or a tech tip that goes through the proper way to tighten the bolts on the front end to get proper geometry.

[NemisusDM]

Thanks for the info guys. I will check everything upfront and see if I get a carb sync too.