Thank you. On the needle valve side, how do I know how much to push the spring down with the top bolt?
the spring tension is probably be problematic now if you don’t already know what the setting is. You were supposed to count the number of turns to fully seat the top bolt down before removing it, so you know how tight it should be. Now you can only guess.
do you know if this is a quick/rapid lift jack or a regular one? I can’t tell based on numbers alone or your description what kind of jack it is - because you’re going to need to know if that needle valve is for a rapid lift or if it is the safety/overload/relief valve.
if it is the safety/overload/relief valve, if you don’t know how tight it’s supposed to be, IIRC, user hiball on here used to suggest seating the bolt completely down, and then backing off 1.5 to 2 turns. If this bolt is too tight, your jack will lift more than its rated 3.5 ton capacity and you will risk blowing seals etc. if the bolt is too loose, your jack will lift less than its rated capacity, often with a fairly characteristic “whoosh” sound of the valve opening to bypass when it reaches whatever limit you have it set. Ideally, you would like to set it so that it will lift 3.5 tons, and then bypass (”whoosh”) above 3.5 tons. You are probably safer, if you set this too loose and know that your jack won’t reach the full 3.5 tons before bypassing, rather than too tight and thus exceeding the jacks rated capacity.
if it is for the rapid lift jack valve, then:
if it is too loose, you won’t have rapid lift. I.e the jack will be slow to raise always.
if it is too tight, the rapid lift will be present, but when it touches a load, it will become much harder/more effort to pump up to lift the load, as it’s still trying to rapid lift the load.
just right is when you have rapid lift, but then the jack slows down its lift when it hits a load allowing for more hydraulic leverage.
here, you are also safer being too loose and losing the rapid lift function, rather than too tight as that could blow the seals in the rapid lift system.
I hope that made sense.
28:40 of this video shows the guy counting the screw rotations to know how tight to make it during re-assembly. Not your jack, but same concept:
