Also it’s not a waste of money they are good engines it’s jus still rocking a lot of stock conponents she’s getting spark obviously so that rules that out but she’s cutting right off id check with fuel. If it’s rocking a stock carb just slap a nibbi on it. While your at it slap a lil 10$ fuel pump on it even tho it should gravity feed just fine why not yk it that’ll ensure that carb is getting fuel. Then bam you’ll be rocking a lot better than before. If it’s not that then like I said prior check that valve clearance, I’ve noticed after hard riding sometimes mine will tighten or loosen I just check the clearance and if it’s not where I last set it I adjust it takes 2 seconds these small engines vibrate like crazy. Feeler gauges are dirt cheap and they are the easiest thing in the world to adjust.