Is it a Honda TS50?
There are a couple of brands with a TS50, I know how to derestrict a Honda TS50 ... but I'm advising against it, the Honda TS50 is a real beauty and they're about 30 years old (they last forever!), Making it go faster will wear the engine much faster and the pushrods in the TS50 engine don't like that at all ... The value of the Honda TS50 is going up all the time, it's becoming a real collerters item, so I'd be good to it if I were you.
Let me see if I can find a picture of a TS50 ... here's a link to a picture of a blue TS50:
The exhaust on this one isn't original.