How do you inflate the rear tire on an E300 Scooter?

1. rotate the rear wheel until the hole in the sprocket lines up with the tyre valve.
2. insert the tyre valve extension through the hole and attach it to the tyre valve
3. inflate the tyre to the correct pressure (usually 45psi)
4. remove valve extension and put in a safe place for next time.

Inflating the rear tyre is detailed in the owners manual, which you can download from the Razor web site.
http://www.razor.com/au/products/electric-scooters/e300/

I posted a similar issue about the same scooter. If you do replace the batteries and still experience the same issue, check the wiring for loose wires and possibly replace the fuse.
After replacing the fuse and connecting wires, my scooter doesn't pop the fues with every use anymore.

http://www.fixya.com/support/t7752702-ride_scooter_turns_off

This scooter may have air free tires not requiring any inflation. This type of tire has foam in the tire and is maintenance free. Look for a air inflation nozzle coming out of the tire. If you don't see one the tire is air free. If you do have a nozzle, then you can add air up to the maximum inflation pressure written on the side of the tire. Hope this helps.

Just buy a new rear wheel. The wheel is not meant to come apart without breaking a couple fingers in return. Besides the new tube is about 15 dollars add the shipping and for another 20 dollars you can get it brand new complete, wheel, tube, rim, axle. I'm not saying it can't be done but why put yourself through this.

sounds like you need a new rear wheel as the wheel locking mech has been stripped or damaged where the cog is at. Can you move the wheel forward and backward with out the chain moving? If so that is your problem.

If the sprocket and chain turn on the rear wheel, it sounds like the freewheel on the rear tire is faulty.

Hi
Deflate the tire and then you can gently move the valve to a straight up position. Now refill the tube.

I just did this a couple hours ago. taking off back tire will not help you. The rotor is attached to the wheel itself. You need to line up the hole in the rotor with the valve stem. You will need to have a screw on extension to valve stem ( I got lucky and had one). Screw the extension onto the valve stem then use air compressor to air up the tire.

Most electric mobility scooters with inflatable tires require a tire pressure of 30-35 psi (be sure to check the manual of your scooter for the correct tire pressure). Do not allow the tires to become under-inflated or over-inflated. Under-inflated tires could make the scooter unstable and over-inflated tires can burst under pressure. Also, you should manually inspect the tires periodically to make sure they haven't taken any serious damage that could lead to a flat.