amcharts Line with multiple value axes

HTML

<script src="http://www.amcharts.com/lib/amcharts.js" type="text/javascript"></script>
<div id="chartdiv" style="width: 100%; height: 362px;"></div>

JavaScript

var chart;
var chartData = [];


// generate some random data, quite different range
function generateChartData() {
    var firstDate = new Date();
    firstDate.setDate(firstDate.getDate() - 50);

    for (var i = 0; i < 50; i++) {
        var newDate = new Date(firstDate);
        newDate.setDate(newDate.getDate() + i);

        var visits = Math.round(Math.random() * 40) + 100;
        var hits = Math.round(Math.random() * 80) + 500;
        var views = Math.round(Math.random() * 6000);

        chartData.push({
            date: newDate,
            visits: visits,
            hits: hits,
            views: views
        });
    }
}

// this method is called when chart is first inited as we listen for "dataUpdated" event
function zoomChart() {
    // different zoom methods can be used - zoomToIndexes, zoomToDates, zoomToCategoryValues
    chart.zoomToIndexes(10, 20);
}

// create chart
AmCharts.ready(function() {
    // generate some random data first
    generateChartData();

    // SERIAL CHART    
    chart = new AmCharts.AmSerialChart();
    chart.marginTop = 0;
    chart.autoMarginOffset = 5;
    chart.pathToImages = "http://www.amcharts.com/lib/images/";
    chart.zoomOutButton = {
        backgroundColor: '#000000',
        backgroundAlpha: 0.15
    };
    chart.dataProvider = chartData;
    chart.categoryField = "date";
    
    // listen for "dataUpdated" event (fired when chart is inited) and call zoomChart method when it happens
    chart.addListener("dataUpdated", zoomChart);

    // AXES
    // category                
    var categoryAxis = chart.categoryAxis;
    categoryAxis.parseDates = true; // as our data is date-based, we set parseDates to true
    categoryAxis.minPeriod = "DD"; // our data is daily, so we set minPeriod to DD
    categoryAxis.dashLength = 2;
    categoryAxis.gridAlpha = 0.15;
    categoryAxis.axisColor = "#DADADA";

    // first value axis (on the left)
    var valueAxis1 = new AmCharts.ValueAxis();
   ...