[DaveJ]

Mark,
Thanks for your reply. I was in my local Yamaha/KTM dealer (the only bike dealer in town) looking at a KTM mini for my son and started talking about my WOT problem. He also suggested trying to go leaner. Monday I am going to pick up a few more main jets and try it out. In the other jetting thread it was mentioned that 178/180 is right in the ballpark for these bikes yet you had good luck with a 160 in a 300cc bike.....I am getting a little confused as to what is going to be too lean or too rich.
BTW, switching to the bigger 180 main improved the midrange throttle but still had the WOT stumble. I also installed my new FMF silencer/spark arrestor (which sounds just as quiet as the stocker) and the stumble is still there so definately not related to that.
I live at about 500' above sea level if that helps any.