What is the size of the furnace, your location, and the size of the house. My first thoughts is the furnace is over sized and is short cycling.

...what Mike said, plus, poor or leaky ducts cause a lot of problems for modulating furnaces. What is the minimum and maximum input on the furnace?

Thanks for your comments as well, Jackfre.
Minimum output 21,000, maximum 60,000.
Model YP9C060B12MP12C.
Janez

Your run times may improve, meaning get longer as the season gets colder. In thinking about it, it is not uncommon for a modulating unit to cycle on and off in the early season. With a minimum of 21,000 that is pretty good low fire rate. Monitor it for a while and see how the run times change with the weather.

Yeah it's very unlikely that furnace is oversized, and even if by chance your house is tiny and extremely well insulated and it is somewhat oversized, can't blame the contractor since that's the smallest modulating furnace York makes.

Are you using the York communicating thermostat with that or a different thermostat? When you stand next to the furnace and listen to it, do you hear it modulate during those 10 minutes? Granted, it's pretty hard to notice small changes in blower speed and firing rate, but the difference in noise level between the lower and higher ends of the range should be pretty apparent.

I agree, it being October and still mild in most places you will probably notice a difference as you head into the winter.