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Yanmar VIO pressure relief for PTO valve

fast_st

Senior Member
Joined
Dec 1, 2010
Messages
1,468
Location
Mass
Occupation
IT systems admin
So the Yanmar vio70 has a fairly kickass hydraulic system there's a PTO valve that on this machine was set up to run the tilt bucket. I opted to put a thumb on the stick as that'll be something I can use a lot of! Anyway after a small mishap, I went looking on how to reduce the pressure on this PTO circuit. There are quarter turn valves on the boom that are great when changing hoses etc, what a nice feature! On the valve for this function, there seem to be two kinds of inserts, the one I have uses a 6mm allen head bolt, 12mm locknut and when you reduce the tension on the bolt, it must just open a valve bypass, I can use it to limit the max pressure and allow the thumb to collapse back under bucket pressure but it ends up with 0 holding pressure. The parts book calls out two valve inserts

172422-74900 Valve Assy, Relief
172146-74720 Valve Assy, Shutoff

I'm guessing I have the shutoff valves

Anyone have a good picture of a relief valve? loosening the allen screw drops the pressure and there looks like a small short piston inside that can get pushed back. Logic says the relief would have a screw and a spring in there to adjust the tension versus adjusting the clearance. Calculating area and pressure and spring tension could be done but finding the correct insert would be better.
 

fast_st

Senior Member
Joined
Dec 1, 2010
Messages
1,468
Location
Mass
Occupation
IT systems admin
So called the dealer today after much unsuccessful shopping online. They had to call a couple places to find one that's a week away, it seems to be a returnable part in case its what I already have. My thought is that its a simple part and not worth $350 clams. I have a lathe and know my way around making stuff.
 
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