For the time being the properties can be set through the chartObject. For example:

ASPX:

        <script>
            function pageLoad() {
                var chart = $find("<%=RadHtmlChart1.ClientID%>");
                chart._chartObject.options.valueAxis.max = 100;
                chart._chartObject.options.valueAxis.min = 10;
                chart.repaint();
            }
        </script>
        <telerik:RadHtmlChart ID="RadHtmlChart1" runat="server">
            <PlotArea>
                <Series>
                    <telerik:RadarColumnSeries DataFieldY="yValues">
                    </telerik:RadarColumnSeries>
                </Series>
                <XAxis DataLabelsField="xValues"></XAxis>
                <YAxis MinValue="10" MaxValue="100"></YAxis>
            </PlotArea>
        </telerik:RadHtmlChart>

C#:

    protected void Page_Load(object sender, EventArgs e)
    {
        RadHtmlChart1.DataSource = GetData();
        RadHtmlChart1.DataBind();
    }
    protected DataTable GetData()
    {
        DataTable dt = new DataTable();

        dt.Columns.Add("ID", typeof(int));
        dt.Columns.Add("yValues", typeof(int));
        dt.Columns.Add("xValues", typeof(string));

        dt.Rows.Add(1, 12, 20);
        dt.Rows.Add(2, 15, 40);
        dt.Rows.Add(3, 16, 60);
        dt.Rows.Add(4, 14, 80);
        dt.Rows.Add(5, 17, 100);

        return dt;
    }