handlebar

I just bought a kit and decided to install it on a new bicycle for myself. I've instalked for people but never owned a motorized bicycle. My question is about a throttle assembly. I bought a new Scwinn Solara road bicycle and it has the curved racing numerous speed handlebars on it. Picture is...

I have just bought a kit (crappy one from china).. we have the engine mounted, and now when we try to put on the throttle, it is WAY too big for the handle bars, but heres the confusing part, the left handle fits perfectly. Am i missing something? Any help is appreciated a ton!