Razor's MX500 scooter is a small motorized scooter designed to look and act like a miniature off-road motorcycle. In order to extend the scooter's range, the MX500 is fitted with a bicycle-type freewheel on the rear axle, so that it may coast like a bicycle does when slowing down. However, many users have run into problems in which the freewheel stops working, so it no longer propels the scooter forward. Luckily, the freewheel can be replaced with a regular bicycle-type freewheel using bicycle tools, saving you the hassle and money of replacing the entire scooter.
Set the scooter on its side on a workbench or other flat surface so that you can loosen the rear wheel without it falling over or being damaged.
Loosen the drive-side and nondrive-side axle nuts using a 15mm wrench. Pull the wheel down out of the frame dropouts to remove it from the scooter.
Set a BMX freewheel remover in place over the freewheel on the rear wheel axle. Using an adjustable wrench, twist the freewheel remover counter-clockwise. The freewheel will begin to disengage from the wheel hub. Continue turning the freewheel remover until you can pull the freewheel away from the hub completely.
Thread the new freewheel onto the rear wheel hub by turning it clockwise. Thread the freewheel on until it is hand-tight. There is no need to tighten the freewheel excessively, as it will tighten as soon as the chain applies torque to it when riding.
Wrap the chain around the freewheel and slide the wheel back up into the frame dropouts. Tighten the axle nuts using a 15mm wrench to secure the wheel in place.
Take the scooter out for a short test ride. Afterward, inspect the new freewheel for side-to-side play or wiggling. If the freewheel is still solidly in place on the hub, the scooter is fixed, and can now be ridden without worry. If the freewheel wobbles from side to side when pushed, the hub of the rear wheel may be bad, and should be inspected by a Razor scooter technician.
