These engines, and the 3hp (very very similar) came on many minibikes. They are dead simple and generally run well. Your engine looks to be produced from 1980-1990, because of the black coloring and more modern decals. Your motor has the VACCU-JET carburator, which are the simplest Briggs and Stratton carbs to work on.
If you'd like any information regarding the exact year and model, look on the cooling shroud, next to where the carb bolts onto the engine :thumbsup:
Good, reliable, bulletproof engines that were found on a variety of classic minibikes. Parts are cheap and usually easy to acquire.
-Jack