battleax wrote:
One thing that comes to mind is the seat that the ball sets on, people recut the seat or lap the seat with abrasives.
As in a poppet valve the narrower the contact area of the seat the better.
When I do check valves I leave the stock configuration alone and use a light polishing compound to clean the seat.
I think any changing the original configuration is a mistake.
Also if your check valves are working properly you should not be filling your crankcase. But I don't think there are many check valves that are 100% effective.
The reason these valves still leak after being cleaned is usually corrosion pits on either the ball, or brass seat, or both. The offending pits can easily be seen using a 10X magnifying glass.
Both the Gentlemen (Darth and 12dot) who offer check valve overhaul services are well aware of the need to maintain a narrow seat for proper ball sealing. As such the seat is re-cut and narrowed during the rebuild. New balls and springs are used hence increasing the cracking pressure to meet Kaw's latest specifications.
Properly serviced lines should not leak at all at rest. They will continue to do so for a very long time if kept full of oil having sufficient anti corrosion properties.
J