Hey Philip... I don't have direct experience with the CR, but on my YZ and KX 80's, I had to drop down a heat range on the plug to prevent fouling. So if the stock plug is a 9, then try an 8. On the low end bog, have you raised the clip on the needle and went to a smaller pilot jet already and it still bogs? Check your air screw. When the bike is at an idle, how many turns out is the air screw to get the rpm sound at it's max? Also maybe fiddle with the idle and see if that helps some. Good luck!