Hi all I’m new to this forum (hi) I’m looking for help/advise. My sons. Bike was running fine until it would cut out every now and then.then just wouldn’t start at all we tried so long the battery went flat .we got it charged up but still not starting so removed carb cleaned it all out. Jets etc. Changed spark plug then it started fir a few seconds and cut out again. We have fuel AND a good spark Any help would be greatly appreciated ?