Why won't MX 900 turn on even after putting in new batteries

Your remote needs to be cleaned internally.

Try removing the batteries, then short out the terminals in the remote. This should discharge any residual power in the components in the remote. Re insert the batteries and it should then work ok

You should set up the remote control with the set-up codes to your device brand.
Check the remote control for its infrared emission. Check it with fresh batteries. If you wish to get more details about how to check a remote control, please visit this site. One among the posts has details about it. Surf the site in "Mosaic" or "Magazine" view. It will make surf easier.
http://electronicshelponline.blogspot.com/
If remote control is found OK, and have infrared emission, set it up with your device by using the set-up codes.
If you wish to get more details; check the sites linked here. It has set-up code list & set-up procedure to many popular brand remote controls. Common codes used for devices too are given, in the order of device brand name list in alphabetical order. Do a search by type in the brand name of your device, at its search box, and press "Enter". Or, pull up older posts.
http://remotesearch.blogspot.com/
http://electrohelponline.blogspot.com/

I think you are talking about an electric motor on your bike . If the motor is New you may have a bad throttle switch . You can use an ohm meter to check the throttle switch . Connect the two leads of the ohm meter to the wires of the throttle switch ( dissconected) . As you turn the throttle the ohm reading should coraspond to how much you turn it .

mine is doing the same thing have you gotten yours to work yet?

Usually when the brushes won't turn it is due to a bad turbine. Insert a screwdriver into the square hole that the pin on the brush fits into, and see if it turns. If it is seized up, the turbine assembly will need to be replaced.

Do you favorite search engine and type your model number and then batteries. What I got is www.buy.com

Turn off CPU, Unplug Power cable, And all usb devices, let it sit for about 20mins. Plug it all back in. Turn on the CPU! Also make sure if your device requires "DRIVERS" or if you have a CD download and install that before anything.

you might want to reprogram it with different codes. it's a classic problem.