I have a late model, not sure of the year, M6800 with V3300-E6 engine, the engine has just a touch over 3,000 hours. I bought it used, in good shape. The problem I'm trying to figure out is that it has a loose valve lash "smack" and almost a knock sound when running. I removed the valve cover to make sure there wasn't a VERY loose valve rocker, which all appear to close to the same. I am going to adjust the valves anyways just to be sure as soon as the service manual arrives. But what I did find has me confused and concerned, all the exhaust valve springs are very spongy. By spongy I mean I can compress the exhaust valve about halfway open with one finger and maybe 5lbs of pressure. I've been a mechanic for years and have never seen anything like this. Is this normal for Kubota or do I have a problem?