My sons razor E300 duns only at about 2 mph on a full charge. Its only been use MAYBE 20 hours over last 1.5 years and has never had any problems til now. The brake is not overly tight, the chain is lubed etc. Don't know what it can possibly be. Help anyone?

You can diagnose your scooter's issues with a volt meter.

test the batteries and make sure that they are putting out sufficient voltage/amperage.

Test the Throttle to see if the regulator is working smoothly.

Test the Controller to ensure that it is working properly, as this is the scooter's "brain".

Check the fuse(s) to ensure that you are connected, and also check wiring for broken, shredded, or burnt wires.

Most likely you need new batteries. If you leave SLA batteries in storage for too long, without use, the batteries lose their charge holding capabilities. SLA batteries hold a charge through a chemical reaction in the Acid Liquid in the batteries. If the chemical reaction settles, the batteries will not accept a charge anymore.

Generally, you don't want to leave SLA battery powered scooters unused for much longer than 3 weeks. :)

-Jackson
http://urbanscooters.com/

Dead battery. You must follow the proper battery maintenance procedures in order to prevent that from happening. Most likely the battery has sat for an extended period of time and has dried out.