Long time reader but first time poster. I need advice here. Been riding my 98 xr400 for about 8 years now and love it, except when it isn't running right. Like now . I am getting her ready for spring riding so i cleaned out the carb (clean, blow out, pressure test), poured in new clean gas, new plug and fired her up. I adjusted the pilot jet and then the valves. She starts up within 8 kicks cold and idles fine. But when i open up the throttle she" pops" and "spits". Hard acceleration cleans it up but then when i am just riding at a steady throttle opening she bucks and pops. This happens in any gear at any speed. I am basically out of ideas. Any help would be greatly appreciated!