No, there aren't. But don't take my word for it. See for yourself.
List of English Irregular Verbs
are there any irregular verbs that start with the letters, "j,n,v,x,y,z"
You might be able to form one with a prefix or something, but I can't think of any.
But our list is complete, including those irregular verbs starting with out-, over-, pre-, re-, un-, and under-.
I bet there is one out there somewhere, hidden away in the darkest recesses of the OED, unused since 1728.