Hi.. My son bought a Suzuki Streetmagic with a 70cc Polini Cylinder kit on. It was driving fine for a couple of days, but then suddenly it would not go to high rpm's without going out. The sparkplug was completly black. We exchange it and was runing fine for a while, but then the piston rings suddenly broke. The psiton has burned oil on top, not carbon. Is it getting to hot ?? how to get temp down ?? Thanks..