Scooter idle issues

[50scoot]

So for as long as i've had my scooter i've always been fighting an issue. When i goose the throttle the rpms come up like they should but then when they come down they go below the normal idle and sometimes it dies most of the time it stays running but drops really low then slowly comes back up? what causes this? idle mixture is off? too much fuel then when the rpms drop it throws the ratio off? The only way to compensate for the rpm drop when goosing the throttle is to idle it really high