Motorcycle Repair: bike is not revving correctly, valuble resource, spark plug wire

Question
I recently purhased a 81 honda xl 185s that seems to run and idle great except that when i turn the throttle it sputters like its not getting enough gas. The fastest I can get it to go is 40mph but it is suppose to go 71mph. I had carb cleaned, but the bike still wont perform right. Plus, it always starts first kick, no problem. I just cant get the power  I know it should. Please, please help! I appreciate your time and this site is a valuble resource.

Answer
Richard, This could be a hard problem to diagnose. If the carb is set right then it could be the pulse generator or the Ignition module which can allow to start and idle but not rev up. Also check the spark plug and see if its the correct one and the resistor cap on the spark plug wire isnt shorting out.