I have done this and it's not working
$("#txtLowValue").val('');
$("#txtLowValue").val();
and this is the text box
$('#txtLowValue').kendoNumericTextBox({
format: "##",
decimals: 0,
spinners: false,
min: 0,
max: 999998
});
Here is a simple example for you to test.
The important bit is this:
$('#txtLowValue').data("kendoNumericTextBox").value(null);
here is a link to the api documentation: value