e-Ton viper 150 - doesn't move forward. Belt is slipping - took apart. Pictures. Help
 

Okay, so my sister have an e-Ton 150. It should be fairly fast.
Since we bought it, it didn't move forward. It hesitated!

I WILL move reverse nicely..


I took apart the piece where the belt is.

I see a belt, with ridges.

The part to the left, is smooth.

I held the belt. Turned the smooth pulley. It slipped.

I KNOW it's not supposed to do that.

Wouldn't that pulley have teeth on?

I will upload pictures.

Tell me how to fix this! We NEVER rode this four-wheeler with it's full potential. My electric scooter went faster than this thing. The engine is fairly large, but the speed and strength is weak.