Desperate for help replacing SCV on a JD 850

[cebrown5]

Might have made a mistake helping my neighbor out. The SCV on his JD 850/ with PS is worn out and no longer available. I had seen a post about replacing it with a more modern joystick valve so I bought one from Surplus Center. 2 SPOOL COMPACT 10 GPM JOYSTICK CONTROL VALVE
I can understand the 4 ports for the cylinders. On the old SCV there is a inlet, a outlet and a line to the rockshaft that I believe they are calling a power beyond line. My understanding from the book is that when the spools are centered in the SCV it bypass's the fluid to the rockshaft, then if its not being used it then returns the fluid to the trans. case.
I bought the valve and also got the power beyond kit for it. I had thought that all I had to do was plumb up the inlet, outlet and P/B (power beyond) ports like the old valve. The P/B kit is nothing but a fitting that you screw into the valve and then hook the line to it. But you also had to install a low pressure tank hose to the #8 SAE tank port. Attached is a picture of the instructions.

To say the least, I am now kind of lost on what to do. This is the first time I have ever tried this and do not want to screw up the mans tractor. I have already spent over $400 on this and need some advice on plumbing this, would be greatly appreciated.

 

[J_J]

You seem to have done everything right.

The tank line goes to any return line or just goes to tank. The tank line dumps the cyl expended fluid

The PB , POwer Beyond passes the fluid to the next valve.

Is the valve marked as to IN OUT/tank, PB, and 4 work ports..

Just make sure the out hose from the pump goes to the IN port of the loader valve.

 

[cebrown5]

You seem to have done everything right.

The tank line goes to any return line or just goes to tank. The tank line dumps the cyl expended fluid

The PB , POwer Beyond passes the fluid to the next valve.

Is the valve marked as to IN OUT/tank, PB, and 4 work ports..

Just make sure the out hose from the pump goes to the IN port of the loader valve.

The valve has a in, out and PB. My problem is that I am having to use the pipes that went to the original SCV. I know which ones are which, just wondering about the PB. According to the book the original will by pass the SCV when operating the rockshaft, don't know if this valve will do the same. It also mentioned about a closed or open system which I don't know what they are talking about.

 

[J_J]

The Kubota hyd system is an open center hyd system.

Closed hyd system do not use PB.

The PB is the line that goes to the 3pt.

Your flow path should be from pump to loader , to 3pt, then tank.

 

[cebrown5]

Got it plumbed up and running, everything works. The only problem that I see is that the loader works so slow compared to when it was working off of the SCV. This tractor has the larger 11cc pump on it, I had replaced it about 8 months ago. I know the filter is good, I had serviced this tractor just two months ago and had cleaned the screen, replaced the filter and put in new oil. I wonder if the new spool valve could cause this?

 

[J_J]

If you matched the valve with the GPM's, and the hoses are the same, the loader should move equal or faster with the larger pump.

Engine rpm dictate the pumps GPM.

Did you check and/or reset the relief valve?

If you really want to know for sure what the flow rate is, take it to a hyd shop and have them put a flow meter in the hyd system, and it will tell you the actual GPM's flowing at an speed.

Does your tractor have a screen in the sump, and if so, clean it also.