As mentioned already, the same lever raises the deck and the 3pt arms. You can lock the deck up, so you can lower and raise the 3pt without the mower moving, by setting the deck height knob under the seat at the floor to "Top". The other knob is the flow rate knob which will control how slowly or quickly it will move depending on how much you close it. If you close it all the way, it won't move at all. It sounds like that is frozen right now, but not in the closed position if the deck is moving up and down - it is not closed.
Sometimes if the flow control is set quite closed (mower deck moves up and down slowly), the 3pt arms will hardly move without something attached, as there is just no weight to pull them down. Try moving your control lever to lower the deck, and put your hand on one of the 3pt arms and press down. See if the arms move down once you put weight on it.
If they still do not move down, make sure they haven't been locked (pinned) in the up position. It's possible the previous owner locked them up if he was just using the deck, and didn't want the arms to move up and down with the deck. To lock the arms in the up position is a different thing - you use a pair of tabs on the frame up by the 3pt arms with a hole in them, and pin the arms up. I'll see if I can find a picture, but if you look back there is should be pretty obvious if the arms are pinned into those tabs.
-- I have a
BX2200 and 2
B2150's. As GolfAddict and others said , all of them have a single control lever for raising and lowering the 3pt hitch
and the belly mower. There is no separate hydraulic system for the two functions.
-- All these smaller Kubotas have a kind of make-shift rod (seems like flimsy design to me, but it works) running from a piece of sheet metal hanging over the 3pt lower arms forward to levers that then raise the MMM deck. Notice I said raise, I did not say lower.
-- Virtually none of the tractors these days have dual acting hydraulics that force things downward as well as lift them up. I have an old Massey Harris Pacer that does both, but these Kubota's sure don't.
The result is that anything going downward -- be it your rear 3pt lift arms attached to lower arms with an implement on them or your MMM deck are all going down by force of gravity, not hydraulics.
-- OK, so there probably is some way to pin or restrain the two cast iron lift arms from dropping. That is NOT done by any knob or control as someone else had said.
-- As a couple of guys said, just push down on the arms and they will go down; might take some force but not a whole lot. Unless the arms have been fastened up which seems unlikely to me & if they were fastened up you should be able to see that.
-- The fact that you got the "speed of lowering" knob loosened up is great but that was never keeping your arms from lowering in the first place.
By the way, it hasn't been mentioned but DO NOT try to raise or lower your deck with the height setting knob unless the deck is lifted to the uppermost point. The weight of the deck rests on the mechanism that adjusts height except when the deck is fully raised. You will break the plastic height setting knob off trying to move it up or down unless the deck is raised fully (so that the hydraulics is supporting the weight of the deck.)
Good luck with your machine.
