I have a two year old Kubota L3010 which is an outstanding tool/toy which I would highly recommend. However, a couple weeks ago, it started knocking to the point where I towed it back to the barn. Found water in the bowl, so drained it all out and changed the filter. Still did not run right, so had the dealer come get her and check it out as I thought the injectors may have been damaged by the water. They said injectors are fine so they drained the entire fuel system and cleaned it all out. They let it sit out overnite in the rain and checked it again in the morning. Mmmmmm, got water in the fuel, how can that be? After some monkeying around, they checked with Kubota and found that they are having some problems with fuel tanks that leak and allow water in. They are replacing the tank but I thought this info might help someone out there from going crazy trying to troubleshoot a problem. Can't say I know which models have this issue but if you are having similar problems, contact your dealer. Good luck..