While we are on this subject... a couple of observations/questions.
1. If an O-ring (#210 in wolfman's post) is leaking, then the copper seal (= copper washer, #50) must have been leaking as well (or was before reinstalling the delivery valve holder).
2. My experience with an older 6 cyl (S2600) Kubota engine confirmed what Wolfman and others on the forum said: re-torquing a DVH won't necessarily fix a leaking copper seal. (In my case the copper seals were eroded with tiny radial valleys hardly visible without magnification, but maybe un-eroded ones can be torqued successfully.)
3. The S2600 parts list doesn't show an O-ring, only the copper seal.
Can anyone shed some light on what to me seems a bit of a mystery:
Q1. is the function of the O ring really to stop fuel leaking out, or is it to keep rubbish/corrosion from building up in the gap between the DVH and the pump body, which would then fall into the pump when unscrewing the DVH?
Q2. if the O-ring is the fuel seal, why have a copper seal?
Q3. is the O-ring a later improvement on the pump design, or was it always there, just not shown in the S2600 or other parts diagrams?
Does fixing a leaking DVH deserves it's own sticky? The advice from D2Cat, Wolfman, and thepumpguysc (
http://www.orangetractortalks.com/forums/showthread.php?t=38811&highlight=holder) helped me. And according to Messicks this particular DVH is used on 40-50 different tractor models (would be great to be able to translate that to specific engine models, but I haven't figured that out).