Be sure that your fuel valve is flowing plenty of fuel. If it is a teeny trickle that may be enough for slower speeds, but when you get into the higher revs of the engine the carburetor has to deliver more fuel. It can run the float bowl dry if the fuel delivered through the fuel valve is not enough to keep up with the demand.
Also, a weak ignition system can fail at higher RPM's. Check your electrical connections, get rid of the factory plug in connectors and solder/ heat shrink tube them, be sure that the spark plug cap is connected well to the spark plug and spark plug wire, and get an NGK B6HS or BP6HS spark plug.
Also, a weak ignition system can fail at higher RPM's. Check your electrical connections, get rid of the factory plug in connectors and solder/ heat shrink tube them, be sure that the spark plug cap is connected well to the spark plug and spark plug wire, and get an NGK B6HS or BP6HS spark plug.