Hi,
Have you tipped the mower up on its side to clean it maybe? If so its quite likely that oil has run into the exhaust and some has dripped onto the deck and the rest is being burnt off in clouds of smoke when you start the machine. Its a fairly common occurance, if you check the oil level in the engine then run it for 10 mins you should find the smoke will clear and problem will be solved. Quantum XTE is also just the model of briggs and stratton engine not the actual model of the mower which will be on a small plate attached to the mower. (behind the engine usually)
mowerguru
September 2009