Razor e300 scooter runs fine but makes a knocking noise when running.

it will run slow for 40 mins at a slow speed, after 15 mins of running fast, the batteries get too hot

Well how long between runs and stops? Batteries can be bad even with 12+ volts on a meter with no load. Is the on/off regular like the controller cycling, or irregular like a damaged wire? The hall sensor in your throttle could be causing it, if it's loose or not working properly. You can open the throttle with a socket and a screwdriver. Check all wiring, check the batteries under load. If you say more about the frequency and duration of the stops and run periods it would help.

No. We get batteries from a local supplier and they work just as well. are by far the most common problem with razors because people dont keep them charged.

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

get some new batteries.
yours are worn out.

it needs a reset button

Neil, I do not have a solution, but however have the same exact problem. Son got an E300 for Christmas. My daughter also received an E200. The E200 works fine, but the E300 makes a clunking noise when the throttle is engaged. Also the E200 can make it easily up the drive way, but the larger and more powerful E300 can not. Any help with this would be greatly appreciated. Thanks, Ron - [email protected]

http://www.razor.com/products/e300-electric-scooter.php