My 07 YZ450F is running pretty rough… During the 30 minutes of break in, the bike sounded and seemed to run great… On my first ride the bike sounded poppy on the bottom end. Top end seemed fine. I pulled the spark plug and it looked tan and on the lean side. The inside of the end of the muffler is black as night with carbon. The bike back fires sometime when I crack it. There also seem to be a ticking sound in the top side of the engine. I thought maybe the jetting was off because of the poppy sound… Now I’m thinking the timing may be off. Any thoughts on this problem?