I will try to give relevant information but anything I leave out feel free to ask..first problem..when you punch the throttle from idle it just dies.It did this with the factory carb, tried tuning it but it was old and leaky and partially stopped up.Bought a new carb ,same problem.I have recently noticed if you put your hand over the end of the muffler and partially block it it revs like it is supposed to..what do I need to check or change to fix this?

second problem, when I installed the new carb I had to adjust the fuel air to get it to start.when it was too rich black smoke and missing.when it was too lean it was cutting out..It seemed to be running great then I noticed the rubber o ring seal between the carb and the intake had fallen out while I was installing the carb..took it back off installed the seal, now the mixture screw seems to do very little if anything..the last half turn putting it in or lean it kills the four wheeler but after that no change..I can even take the screw out..remove the carb diassembled it, nothing was stopped up.all seals looked good.reassembled reinstalled, same thing..tried moving the needle one slot each direction, ran worse both ways.mixture screw still ineffective..any tips would be appreciated.