After about an hour or two of riding I got into some slow 1st gear single track, when I emerged the bike hard a very bad hesitation when I got on the throttle hard. I changed my oil today, used Mobil 1 Gold cap 15w 50. I've always used the red cap but they were out. When I got home it I compared an old Mobil 1 bottle and they appear to be the same, full Synth 15w50 (so maybe the cap just changed colors ). This is the only mod I've done in the last week. Also, I noticed some oil on the left bottom frame. Some if from the oil change but it looks as though some is comming out of a breather hose on that side. Could all these factors be linked? Are they obvious signs that something is going wrong? 4Strokes are rather new to me, I know I need to adjust valves but what else should I do?