Leaving the fuel petcock on should not pose a problem unless the carburetor float valve is bad. Chech your oil level is it higher than the last time that you checked it? does it smell like fuel if not then its ok, is so then its best that you change the oil and get the float valve repaired. Remember that all small engines need their oil checked every day before startup.
ANSWER: leaving the gas petcock on all night will have no effect on your oil what so ever since all Harley have what is called a dry sump oil system. That is, rather then storing the oil in the crank case, the oil is stored in a containor separate from the engine. If you have a weak float valve, the result will be that all your gas will leak out through the carbs over flow vent. If you came out in the morning and there was not a puddle of gas under your bike, then you are just fine to ride it normally. Don't make leaving the petcock open all night a habit though.
How do you change oil on a 2001 sportster 1200
The Harley-Davidson XL1200C Sportster 1200 generates about 68 horsepower. It is the larger version of the Sportster with other being an 800cc.
Not sure about a 1200, but on a 1988 sportster 883 its behind the sealed beam headlamp bulb.
under the seat
Plug gap for the Sportster 883 or 1200 should be .040
harley sportster front axle torque specs
One down, four up.
Out of gas?
4000
39mmx23.5inches
Next to the battery.
3.5 quarts