Harley-Davidson Sportster Motorcycles from 1986 to Present.
Why does my oil light come on when the motor gets warm?
You might want to make sure you are using a straight 30w, or heavier, oil and that the oil is not broken down by heat or contaminated by gas/solvent. If it is not the oil itself, then it could be the sensor (hopefully) or some bearing is getting loose enough to impact the oil pressure when everything's warmed up.
Noah Ackerman 完成的 2016年01月19日
Noah is right.
Another possibility is degraded oil and more probable, a worn oil pump.
( a tooth wheel pump )
Change the oil and look carefully for metal-chips.
Check ( by taking it to pieces ) your oil pump then!
Good luck !