New carb behaves like old carb. Engine starts gets warm, and starts popping back through the muffler.It will die in about 5 minutes If I start it on choke after it dies, it will die when I open the choke. Would a bent fly wheel key do this? Perhaps a stuck valve? The last time I messed with it was 5 yrs ago. If memory serves me, it was acting up then. I'm open to suggestions TIA