Motorcycle Questions? Ask a Mechanic.
It sounds like you might have an air leak around the intake somewhere. I would check for cracks or holes in the boots around the carburetor. You can also try spraying some carb cleaner on the intake boots while running and if the idle goes up then you know you have an air leak. Also be sure to check the condition of your air filter.
You're welcome, feel free to contact me with any additional questions.