Can not access json values from d3 element - d3.js

Question

I have the following d3 tree code I am trying to change. I want to substitute the circle elements with a slightly bigger pie charts that plot from two values in the node's json, namely val1 and val2 as indicated in the image (these values are shown as 20,50 for the root node, for example) . Here is the code originally taken from here:
https://bl.ocks.org/ajschumacher/65eda1df2b0dd2cf616f
Below is the update() method I am changing:
function update(source) {
var nodes = tree.nodes(root).reverse(),
links = tree.links(nodes);
nodes.forEach(function(d) { d.y = d.depth * 180; });
var node = svg.selectAll("g.node")
.data(nodes, function(d) { return d.id || (d.id = ++i); });
var nodeEnter = node.enter().append("g")
.attr("class", "node")
.attr("transform", function(d) { return "translate(" + source.y0 +
"," + source.x0 + ")"; })
.on("click", click);
nodeEnter.append("circle")
.attr("r", 1e-6)
.style("fill", function(d) { return d._children ? "lightsteelblue" :
"#fff"; });
nodeEnter.append("text")
.attr("x", function(d) { return d.children || d._children ? -10 : 10; })
.attr("dy", ".35em")
.attr("text-anchor", function(d) { return d.children || d._children ?
"end" : "start"; })
.text(function(d) { return d.name; })
.style("fill-opacity", 1e-6);
****// append pie element here****
color = d3.scale.category20c();
var vis = nodeEnter.append("g")
.attr("x", function(d) {return d.val1;}) ****// d.val1 is accessible here****
.data(function(d) {
var data = []
data.push({"value": d.val1 }) ****// but here get a type error indicating d is undefined****
data.push({"value": d.val2 })
return [data]
});
var arc = d3.svg.arc().innerRadius(0).outerRadius(10);
var pie = d3.layout.pie().value(function(d) {return d.value;});
var arcs = vis.selectAll("arc")
.data(pie)
.enter()
.append("g")
.attr("class", "arc")
arcs.append("path")
.attr("d", arc)
.attr("fill", function(d, i) { return color(i); } );
}
I have two problems:
The d variable is undefined inside the append method as indicated in the bolded comments above. If I replace d.val1 and d.val2 with hard coded constants the pie renders.
second problem is that only right branch pies render while left branch pies do not even when code is working with constant values for the pie chart.