When you say smoke, do you mean black smoke..? which will be too much fuel (rich) this could be down to float, float valve and or choke, does it have automatic choke.? is the air filter clean.? take out the air filter to see if it runs a little better, if so clean or renew it but do not mow without one in. post up the engine make and numbers that are on the engine, but before you do anything to it remember its new so have a word with the dealer.