I converted my firestorm to the hpi rotostart system from the day i had received my firestorm. Since i already had the rotostart because i came with my rs4 i only had to by the parts you fix on the back of the engine. It works well i never had problem with it ! I think it is easier to prime the engine with a rotostar that ith a pull start system unless the fuel thank has a very goood primer !