dreazoian

I recently got a 49cc pocket bike and when i bought it the lady said it had been sitting for 2 years but i ended up getting it started on like the 10th pull. i lifted the rear wheel and gave it gas and it seemed to spin okay. I couldnt ride it because the tire was flat. I took it home pumped up the tire and when i wanted to ride it, i noticed i would give it gas and it would go like 3mph. I tuned the carb and it went to like 5mph. I noticed the clutch wasnt functioning like it should so i went and bought a new clutch identical to the old one and put it in, retuned carb again and still no difference. What is the problem? is it the wrong clutch? do i need to clean the carb? ive also tried lettting it idle for a little bit to get warmed up but nothing helps. And now i cant even get it started.