I have experience with 3 T-15 engines of one of my friends all of them where new. One ran fine and the other two I had to seal the engine for them to run properly or even stay running as they where sucking air. All so if you have the stock tank with the primer they are notorious for sucking air and is why most go to the race tank with out the primer as if it is not sucking air it will sooner or later. I am sorry to say the T-15 is not the best engine and I hate saying that, as I am a HPI person. This many not be your problem just want to give you a heads up.