2006 YZ450F: POPS AND BOGS Dear MXA. My 2006 YZ450F pops at low rpm, when decelerating with the throttle off and it doesn't want to idle. Also, it won't start without choke even when warm. Have you guys experienced something similar with this model? Your problem is not uncommon and the fix is relatively simple. The standard pilot is 42. We have had luck fixing this problem with a 45, 48 or 50 pilot jet. The choice depends on how severe the problem is (you be the judge). We would start with a 48, since summer is coming, but order a 50 pilot for winter.