If I give the bike more then 1/3 throttle, the engine bogs down and won't give me much if any power. I changed the spark plug and drained the petcock on the carburetor. What else can I do to get this running smoothly?
your hi speed jet is clogged, or float isnt functioning all the way or the brain/points depending on bike type needs replaced, or coil/spark plug wires are failing. trouble shoot these 1 at a time and you'll get there.
(Check spark firs, its free and cheap, then clean carb)