I have a 1999 Venture and have noticed on occassion that a small amount of coolant leaks from these rubber drain plugs behind the covers on the cylinders. Does anyone have more information, like Yamaha part numbers to order these? And looks like they pull out easily, so probably not too big of a project, just top up the coolant at the end. I have read that a dime will add some extra pressure to stop the leaks but since the bike is from 1999, I want to replace all 4.