Yes, Welcome aboard!
Geez, hate to hear about your issue with your scoot's rough ride above 40mph.
If you are on the same road, with identical scoots, same tires and PSI in the tires - and yours shakes and his doesn't - yes, please do keep us abreast of the service findings.
Recently here, had a fellow complaining about his 'egg shaped' tires bouncing at speed on his new scoot. He was thinking of having a good set of Michelins put on.
Do the dealers do a full-blown hi-speed spin ballance with our tires - or is a static "see which side drops and add a weight to the other side" kinda ballance?
Wonder if it's your Kenda tire, which might take the high-speed spin to pick up an issue?
Seems like you could spot a head bearing issue by just taking hold of the front forks and looking for movement.
Does friend's scoot have significantly more miles on it than yours? Lot of guys here say their scoot runs better with a couple thou miles on it......although mine was fine from the get-go.
Anyway, I'm a carpenter not a mechanic.
Do keep us posted - and hope you get back to a perfect scooter riding experience (as perfect as it can be with cars out there with us)
Stig in Ohio wildlands