Michelin Power tire?
 

Got around to changing the front tire. 2007 Reflex with OE Bridgestone tire, @ 8k miles. Some tread left but feathered wear so what the hell I'd change it.
Got a Michelin Power, identical size 110/90/13. First couple days of riding were rain days and all seemed fine.
Today's commute was hot & dry, so at 70mph and above I find that the front end is dancing, and not in a good way. The bars gyrate back and forth. It seems to be set off by turbulence or by bumps in the road. The faster you go the worse it gets.
The thing is this never happened till the front tire change. Anyone had this result after a new front tire change?
Checked to be sure the tire direction is correct, and the ballance seems ok, but not checked on any machine.

If you don't balance the tire, use something like dyna beads in tire?

Just suggestions, but you don't ride fast in rain, you do when dry. Sounds like balance problems...

I have a 2001 Reflex. I changed from the Bridgestone HOOP to the Michelin City Grips about two months ago. The City Grips have a higher speed rating than the Bridgestone. Since I spend most of my time on the freeway the added safety of the higher speed tire was appealing. I thought about buying the tools to change the tire myself but when a local store offered to change the tire and balance it for $20 it was hard to refuse. I have gone over 80 mph on downhills on GPS with the City Grips and they are perfect.

I thought about the Power Pures but there seemed to be agreement that they have a shorter life and might be less capable in the rain. Price wise they were about the same as City Grips but City Grips are supposed to be not as sporty as the Power Pure.

Wish I had I gone with the City Grip first. I decided to fall back on the OE Hoop. Want to ride and wobble at 70+ mph is not fun. Most of my ride is Highway, and 65 is minimum to keep pace. Killing time I checked the steering head, smooth and rechecked the preload, in specification. The bike is not rock steady at 70+mph but never wobbled like after the Power tire install. Hope to get it back to normal soon.

The most common cause of these type of problems I have found is that the rear wheel and the front wheel are not in alignment. The wobble occurs at speed because the rear wheel is a heavy gyroscope and the front wheel is a lighter gyroscope. The higher the speed, the more the heavy gyroscope tries to pull the front gyroscope into alignment with itself.

Here is the solution,

http://www.ex-500.com/index.php/topic,148.0.html

I use a laser instead of string.

My 2001 is stable even when I have gone past 80 downhill. My guess is that the Power Pures probably stick to the road better than the OE Hoops so the rear gyroscope pulls harder to get the front in alignment which makes the wobbles worse.

I got the Bridgestone today. Just looking at the two tires you'd swear they were different sizes. The Michelin is wider and much heavier weight wise. Both are labeled 110/90/13 but look and measure different.
Anyhow, the commute was normal, no shake even at 80mph nearly topped out. I liked the Michelin for feel in the corners but am going to send it back. OE Hoop seems to be a better all around tire on this scoot.

This may not be revalent to your problem but on a motorcycle that sounds like what is called a high-speed wobble. Most of my background is in motorcycles ( not scooters ) In my younger (more foolish ) days , I used to do a lot of street racing (for $ ). I just wanted to tell you that whatever you do- DO NOT hit the brake or you'll definitely take a spill! Even if you feel that you should brake , just ride it out!!!!:s