Hi Folks My 743 sprung a massive hydraulic leak at the boom up/down spool (top spool - left hand pedal). I have removed the spool and found that the screw that connects the spool with the rear spring assembly has sheared off. Possibly this resulted in the seal failure..not sure. I can only see one o-ring on the spool after removing it and it basically looks like an o-ring, it doesn't at all look like a quad-ring. I'm told by parts suppliers that it should have 2 quad-rings....is this true, when I can only see one o-ring? If I do need to add the rear quad-ring, is it best to add it from the front after the spool is replaced, I can't imagine it would push through. I have not removed the cast alloy cover with the circlip. Should I to check the balls/springs? Thanks for any help/advice.