743 low hydraulic flow

[Tazza]

I already know the answer, the pump is worn but just in case i have missed something.....
I sold a 743 a few years back, the owner and I have stayed in contact. He recently wanted a hydraulic motor to convert an old slasher into bobcat mounted slasher so i was asked to get a motor for him. I did all the calculations and decided on a 4.5 cid motor to suit the 11gpm flow. He got it all setup but the motor was turning VERY slow, 200 odd rpm he estimated, he brought it over and i measured it on my machine at 600 when the machine is flat out. At idle mine turned it about the same as his did flat out.
Obviously his flow is down, quite a bit i might add. Any thoughts if i could be missing something other than a worn vane pump? everything else works as it should, backhoe attachment, 4 in 1, auger all work fine. I know they don't require the full 11gpm flow so you really wouldn't notice it that much.

 

[skidsteer.ca]

You would think it would be noticable on his lift and tilt as well if its that much different then yours. 4.5 ci should be close/right displacement.
I run 6.2 on 16.9 gpm to get 540 rpm.
Are you sure his linkage is fully strokeing the spool in the control valve? It should still spin full speed when the attachmanet is not cutting, the pressure in the circuit would be low then.
I don't see how his flow could be down by 50% and him not noticing it with the auger too.
The only way to be sure is to put a flow meter in a loop between his couplers and restrict the flow to 90% of relief pressure and take a flow reading.
Also a worn pump should be good when the oil is cold and lose it as the oil warms
Ken

 

[Tazza]

You would think it would be noticable on his lift and tilt as well if its that much different then yours. 4.5 ci should be close/right displacement.
I run 6.2 on 16.9 gpm to get 540 rpm.
Are you sure his linkage is fully strokeing the spool in the control valve? It should still spin full speed when the attachmanet is not cutting, the pressure in the circuit would be low then.
I don't see how his flow could be down by 50% and him not noticing it with the auger too.
The only way to be sure is to put a flow meter in a loop between his couplers and restrict the flow to 90% of relief pressure and take a flow reading.
Also a worn pump should be good when the oil is cold and lose it as the oil warms
Ken

I thought so too.... But he thinks my arms lift about the same speed, but hard to tell from just looking.
He actually removed the motor and had it on the ground to see the rotational speed, no load at all.
For him to get the flow checked it would potentially cost him more than the pump parts would clost... He needs to hire a trailer at probably 100+ for the day then the cost of the guy to do the test at a shop.
The thing is, if the linkages weren't quite right, i'd have suspected his hoe attachment would run slowly too, but he may not be noticing it.....
Still its an idea, i will put that to him to check, even if he moves the lever to the left instead of detent to the right to see if it speeds up at all. Better to cover all bases.
Thanks for the ideas Ken.