Hi Everyone I need some help I just put a oil cooler from a 88 fz600 on my 87 Yamaha radian direct fit same motor on both bikes my question is, is there a check valve that allows the oil to stay in the oil cooler rad when the bike is shut off? And if so how do you drain the oil from the oil cooler rad when you do an oil chainge to ensure you have almost 100% fresh oil? I thank anyone in advance for there help.