Noob humbled by removeChild

programming flash
1

I have a simple animation that shows bicycle riders going from left to right across a landscape at various speeds. No problem there. I’m pulling the bicycle rider in from the library with addChild. I’ve got a timer set up that repeats 8 times and when each rider leaves the stage I’ve got a conditional statement that sends him right back to the beginning. What I’d like to do is have the timer repeat indefinitely and the rider be removed when it leaves the stage so that new riders are constantly being added at different speeds. I cannot figure out how to remove the rider as it leaves the stage. The code is below. I would uploade the .fla, but it’s twice as large as the limit.


var riderTimer:Timer=new Timer(1000,8);
riderTimer.addEventListener(TimerEvent.TIMER,makeARider);
riderTimer.start();

function makeARider(evt:TimerEvent):void {
    var newRider:mcRider=new mcRider();
    var startingDepth:Number=this.getChildIndex(mcBackground)+1;
    addChildAt(newRider,startingDepth);
    newRider.x=-101;
    newRider.y=6.8;
    var riderSpeed:Number=(Math.random()+1)*20;
    function moveRider(evt:Event):void {
        newRider.x+=riderSpeed;
        if (newRider.x>=644) {
            newRider.x=-101;
//Here is where I'd like to remove the rider movieclip
//I've tried removeChild(newRider); No go.
        }
    }
    newRider.addEventListener(Event.ENTER_FRAME,moveRider);
}

Thanks, as always, in advance.