Update: If that is a 250cc engine, it's a TZR250. The first version of the engine was a YPVS liquid cooled parallel twin with case reed valves. It had to fit in a backbone frame for a race bike so the carbs were low...
yamaha claims 50 BHP @ 10,000RPM. The idea was a road going race bike but that number seems a bit inflated for a stock trim engine that was designed to last any kind of time