valve leaking maybe bad springs

[mark777]

You can not test valve springs by measuring free length. They need to be tested on a valve spring test stand that measures spring resistance at the compressed height.

Exactly!

I must be missing something here...I've done a few Yanmar heads and have never encountered weak springs. I can compress the valve assembly and spring with the palm of my hand after they're assembled. There isn't a radical, or high lift cam, nor high RPM's to cause valve float. Even bent push rods would have the opposite effect of allowing valves to stay open...seems to be one of a few choices. Cracked head/seat, porosity on valve face or seat or a poor grind match between valve faces and seats. All of which would fail a liquid leak through test.

I guess I'm not understanding what's happening.