A friend of mine designed an improved engine breather system for small engines
He sold the rights to several motorcycle companies for fitment to new engines and also made a retrofit kit for older ones.
He spent 5 years researching various check valves & check valve materials before he decided to make his own.
Down side was the rubber diaphragm material was $ 15,000 a sheet so after much hasseling the makers finally told him their customers and he tracked them down to see what they did with their scrap material.
So finally he could make a kit for under $ 100 ( US )
It was not economically viable , not because they did not work, they worked perfectly & I have fitted a dozen or more it was just Joe Public could not see the difference between his kit & installing a couple of off the shelf break valves which cost $ 5 each .
Even as scrap his diaphragms alone worked out at $ 10 a piece and that was just the materials cost .
OTOH it led him to establish a scrap business for exotic ( very expensive ) rubber / plastic composite sheeting which was very profitable .
