JavaScript onkeypress delayed trigger

JavaScript onkeypress delayed trigger

I have an html input for an optional phone number, along with 2 radio
inputs (Leave Message, Dont Leave Message):
<input type="text" class="input-medium phoneNum2" name="secondaryPhone"
id="secondaryPhone" onkeypress="toggleRadio(this)"
onblur="toggleRadio(this)" placeholder="703-555-1010"
value="<cfoutput>#session.secondaryPhone#</cfoutput>" />
Notice I have two events running (deleting one of them yields the same
issue, having both helps out, but I'd rather have only 1 event unless
necessary).
The scenario here is: The second somebody starts typing into the input, it
checks to see if one of the radio buttons is already checked. If not,
default select yes. If for some reason they delete the phone number as
they do not want to give it, both radio buttons should be de-selected
(only the onblur works there). And if the "Don't Leave Message" is
selected BEFORE the user starts typing, it should not default to yes.
Here is the JavaScript:
function toggleRadio(x) {
y = document.getElementById("contactSecondaryYes");
z = document.getElementById("contactSecondaryNo");
if (x.value.length < 1) {
y.checked = false;
z.checked = false;
}
if (x.value.length > 0 && !z.checked) y.checked = true;
}
Now for the issue: The default option yes is only triggered when I type in
2 characters, instead of the desired 1 (almost like a delay in the code?).
If I have "No" Selected before I start typing, it defaults to yes once I
type in the 2 characters. Likewise for reverse, nothing is "de-selected"
when there are 0 characters during the onkeypress event, only when the
input loses focus during the onblur event.
Am I using the wrong events? Is there a logic flaw? There are no error
messages, and no, I cannot use jQuery here, so please don't give me jQuery
answers or the usual "Why no jQuery?" (I love jQuery I simply have reasons
I cannot use it).
Edit: I also tried ordering the JavaScript like this, to no avail.
function toggleRadio(x) {
y = document.getElementById("contactSecondaryYes");
z = document.getElementById("contactSecondaryNo");
if (x.value.length > 0 && !z.checked) y.checked = true;
if (x.value.length < 1) {
y.checked = false;
z.checked = false;
}
}
Basically I want to know why the code is acting like there is a delay, and
is there a way to fix it?