I recently purchased a ct200u ex used and modified it a little bit- stage 1 kit, new spark plug, new gas and oil, lubed up some parts, 18lb valve springs, new carb and carb jet. Athough recently i have not been able to start it up- the pull start will allow itself to be pulled a slight bit but then about halfway or a third of the way thru the pull, the pull start siezes up and wont move. I removed the spark plug and tried to pull the pull start and i worked smoothly- it didnt sieze up. I am inclined to believe it is an issue with the internals of the engine but im not sure exactly what. if anyone has some advice or ideas please tell me.