Hello! So as i have a summer job now i am taking my bikes to work everyday (ironically i work at a bike shop as a mechanic). Anyway a few days ago i tested out my broken in YD100 bike that i made for towing a trailer and put back on my "custom" pocket bike exhaust. Thing is that it has a higher top speed at about 3/4 throttle. I reached 60km/h on a flat. If i try to pull with full throttle it starts 4 stroking like crazy at about 35km/h then if i let of the throttle it pulls and sounds very nice. If i pull the spark plug it is black so this means i am running rich... If i use the stock exhaust it performs good at WOT but it only reaches about 40km/h. Would i solve this by using a smaller jet size? (i will open up the carb and see what size is in it right now). I use the bike at about 350m and the ambient temp of about 20-35 degrees.