Yanmar C50-r2 hydrostatci pump

[Ajmoore1]

Hi Guys,

I have got a converted Yanmar C50r-2 which has been converted to carry a post knocker. Its got three point linkages on the front and rear so a handy bit of kit. I bought it two years ago to carry my protech knocker, I do a bit of agricultural fencing for customers appox 1-2k meters a year so not a massive amount. It has been very handy but has always been weak tracking on one side and i am worried about getting stuck with it. Is ok on the flat but on a bank or tarmac struggles to turn the one way so aways have to use the good side. Its an old machine and i cant justify spending 1000's £ on it but to good to scrap. It has a sundstrand daikin PV2121-504 pump on it which i am finding hard to get any info for. I have got it into the workshop to investigate. Investigation work so far includes :-
1. pressure gauges on both pumps, the bad one was showing 200 bar and the good 350.
2. Swapped the pipes from the pumps to the opposite track motors and the fault shifted. (this confirming the fault is in the rear pump?)
3. Swapped the control valves around on the pumps and the problem didn't move so presume they are ok.

When. i bought the machine it came with a spare pump minus the linking but unfortunately it has got slight corrosion on the inside so buggered but i used that as a reference when stripping down the pump as i have not done one before. I have tried lapping the groove out on 600 grit paper on a glass plate but it does not appear to be reducing. I am struggling to find a replacemnent valve plate, i can find ones for pv21 pumps but the dimensions are different. Internal diameter is larger.

Does anyone know if the valve plate can be lapped or know of anywhere that can do it or have any advice. I have tried a few hydraulic places and the want me to send the whole pump for refurb but unfortunately i am not in the position to do that. Pics of machine and plate attached for reference.

Thanks in advance

.

 

[V8Druid]

try these guys

https://www.whitehouseproductsltd.com/home

 

[Lancs Lad]

Sounds like you’ve done a solid bit of detective work already – swapping the lines and valves was exactly what I would have tried. The pressure drop you’re seeing really does point back to the rear pump.
Valve plates can sometimes be lapped, but once there’s corrosion or deeper wear it’s hard to get them sealing properly again. That’s usually why hydraulic shops push for a full refurb, even if it feels like overkill.
If it helps, there are some useful Yanmar resources and manuals collected here: byte-market.com/make/212-yanmar

When AI can't spell....

 

[Mick-the-fitter]

Swap the two motor parts around giving 275 bar per side

 

[Mick-the-fitter]

Sorry meant pumps!