i have 90k on my gs400 and every time i start to get a shimmy i just balance the tires and it goes away. before digging into other expensive repairs, find someone with a good wheel balancer, that's designed for stick-on weights. don't be afraid to ask them if you can see their balancer. that being said, they also have to know how to use it. my local lexus dealer has a kick !Removed! balancer, but they couldn't balance a go-cart tire.
this is the one i have and its awesome
http://www.accuturn.com/wheel-balancer-1450.html
granted i've had a few years and there's newer ones out now, but like i said, you can have the best equipment but it comes down to the operator.