I have heard of people complaining of Burgmans that are hard to push backwards when running. It may be your transmission dragging. I have a 2009 Burgman 650 with 15,000 miles on it. If it is hard to push or if the motor seems labored when you turn higher RPM's then check the transmission oil level. You can remove the level test bolt without removing any plastic body parts. I checked mine recently and got 30 oz of extra oil above the 12 oz normal fill level. Oil can migrate from the motor at higher speeds and overfill the transmission. The motor now accelerates faster, revs easier, runs with less strain (sounds quieter at speed) and pushes easier. My gas mileage also went up as a result. I was told to check this by a gentleman that has several Burgmans and has had the same problem so I assume it is fairly common. When the transmission overfills with oil the extra drag from the oil creates resistance that puts more strain on the motor and makes the bike harder to push and slower to accelerate. I also noticed that when I let up on the throttle the scooter slowed so fast I hardly ever had to use my brakes except to come to a full stop. All these things are the result of the drag the extra oil puts on the drive train. The scooter now runs better than ever. I will be checking my transmission oil level at every oil change from now on.