So I have a 2006, I bought it last September with 3500 KM on it. Recently (3 months ago) I took it on a longer trip, curvy county blacktops, cruising at between 50 and 60 MPH 150 miles with several breaks. Usually below 6500 rpm. No problems to speak of but the last stop I made I noticed the scoot was louder on acceleration. Almost like the airbox was open. It would quiet down when I settled into cruising speed.
It didn't seem to run any different but the loudness concerned me enough it got a ride home in the back of a pickup. I parked it for a few days and when I had time I gave it a quick once over. It seems like all of the air cleaner connections are secure and the engine sounds fine. It just gets loud under acceleration, kind of a throaty rumble. Again similar to running an open carb with no air cleaner.
Since then I've taken it out on 2 - 40 Mile round trips and put another 800 KM in the city. I have noticed a little hesitation on slow accelerations and maybe the hint of a miss or fuel problem sometimes when at cruising speed. But mostly just the noise.
It doesn't seem to be the muffler but it could be. Also it is getting poorer and poorer fuel economy each time I fill up. I went from 67 MPG city before the trip, the next tank full was 62mpg and today it was 57mpg and I'm driving it more conservatively now than I ever have.
One other thing, and this may sound weird, but since buying the bike I've sensed something loose or grumbly in the drive case. Starts have always had a bit of a slightly jerky feeling.
For full disclosure Prior to the long trip I changed the oil and had two new tires installed.
Any ideas, before I tear into this fairly low mileage bike?