Motorcycle engine oil decreasing periodically

Most motorcycles use oil over time and it's normal, especially as the bike gets miles on it. You didn't say how much it uses or how many actual miles were ridden, but in 1500 miles a quart isn't bad....you actually need to change your oil in 2500-3000 miles anyway. Try using synthetic oil (I prefer Amsoil)....you may have better performance with a high grade oil.