I have a friend with a JD that has a Kawasaki 17hp engine. The oil drain has a valve installed because it is so hard to get to. He has already had two valves installed and both leaked through the valve stem While the valve is closed. There is not any way to remove the valve stem and replace the o-ring. He could buy another valve, but already being 0 for 2 he thinks there is just a problem with the valve design. Has anyone had similar problems that they have solved or found out what the problem is.