Hi, I have a bike with a 66cc engine. It worked fine when I broke it in, just low on power (as they all are). After the first four tanks (16:1) I had my friend/mechanic do engine modifications. He ported everything and put a larger outlet on the muffler. Bike runs much faster and better except it has trouble transitioning from idle to throttle. I stop the bike, it idles, but when I pedal and hit the throttle it makes a small bog and takes like 5 seconds to really get going. When it is in idle and I push the throttle a bit it just bogs and dies. When my friend ported it, he put the pin on the carb needle from the second to third position, making it richer. I decided to take it apart and move it back to the second position, but it did not make a difference! Any solutions to this problem would be much appreciated!