My 2011 ybr125 keeps stalling out. I can leave it ticking over for a while with no issues ,however when I ride the bike it stalls out . Sometimes is 1st , 2 nd or 3 rd if I am lucky.the bike will restart once I let the throttle back to the rest stop. I have change the complete inlet manifold from the head to the air box with no difference. Has any one got any ideas?