Doc on the rtv it works that way....had a 900 now have the 1100....but on the bx 22,23,25 they don't work that way as I own both the tlb23 and the 2350 lawn tractor.
My tlb in low with WOT will pull a lot till you over power the relief valve then it will pull the motor down a little.....backing off the gas does nothing but makes it worse. To get maximum back hoe pressure you have to run WOT or very close to it.....3,000 to 3400 rpm. At idle wont even raise the front end loader unless you give it 1/4 throttle....same with the lawn mower....deck won't raise unless you give it 1/4 throttle.....normal with the this kubota series.
I plow down trees and brush with the front end loader with no problems up to about 3 inches in dia.....he has a problem if he can't even get outs a rut or a steep grade as I have no problem with these at 1/2 throttle in high.
If he has a manual he can take out the relief valve without losing any hyd fluid and see if its broken.
They use shims to adj. the pressure....on mine the back hoe was sorta weak so I bought some from kubota and used the thinest one first and that did the trick...they run in a certain pressure range....but since I don't have all the stuff u need to check it just go slow with shims till you are happy and don't over due it or you will wreck the pump....its a fine line but a .005 shim makes a big diffrence there.
With the back hoe I have dug out 4 foot tree stumps and with the bucket full of dirt if you get a tree root with the boom just right the front wheels come off the ground about 2 feet and when you try to let it down slow you can't and boom there goes your back from the front end hitting the ground. I try not to do that gets old on a 60 old year old back....but once in awhile you hope just little more will break the root.....not always.....lol
Am glad I got the 23 rather than the 25 as they have really down sized the cyl. and pins on the new ones.
A 4 feet tree stump may take 16 hours to dig out so you can bury it under ground tho.....if you have time I just work on it a couple hours a day when I feel like it.
Its a hobby tractor not a money maker thats for sure...but great it tight places were if you need to dig for a 4 or 6 inch line then it might make you a few bucks.
I only use it hard for about 2 or 3 hours at a time as the hyd. temps do start to get hot so I never over due it.....there is always another day.
Sorry I see I rambled on here.....lol
Art