Late-model KTM four-stroke models have the coolant hose fitting at the highest point of the water jacket, so they do not need to have the air bled from the system if it is drained and refilled. The 2000 to 2007 KTM RFS engine has a small bolt on the top of the left radiator, and another on the head to bleed the air from the system. The bolt on the head is the one near the spark plug with a copper sealing-washer under it. Cooling is much improved if the system is bled.