I have a mikuni carb that is hissing a bit and was wondering if anything besides a air leak would cause this? I checked everything with carb cleaner and couldn't get a surge in the idle anywhere. Would too large of an air filter cause this? I'm running the k&n filter that came with it but it looks bigger than the filters I've seen in pictures. It's also a tapered cone not the straight cylinder that everyone seems to be running.

I think you are just hearing the airflow into the carb. If you couldn't find an air leak with the carb cleaner and it is running fine I don't think it would concern me. But that is just me.

Russ