The further back the carb sits on the intake causes the "cam sound", To Check,
Start ped up, loosen carb clamp bolt and push carb forward or back to quite carb "cam sound".(adjust carb while ped is running)
also, if you have any leaks at the intake gasket or carb to intake joint this will cause this sound.
To Check for leaks,
With ped running (from cold start) spray a "Little" WD-40 around any joint and if it bubbles up you have leaks.