Kubota kx91-2 Tracking Issues

[wiggy]

i would google hydraulic pump re builds (ect) there are plenty of companys out there who will re con them
but its not cheap and you might feal like you have had ur pants pulled down and ur legs smaked

or try warwick ward at barnsly they may have broke 1 and b selling spares of
i know there yard is masive its over a mile long although if you go dont look round as there are to many toys there to buy

as a final thought find out ( if you can ) what other makes / models the machine was sold under in this and or other countrys as it makes looking for bits that much easyer
and some machines are just badge technoligey
have u checked suction hose isnt parcaly colasped
also put a magnet on bit of string and slosh it around in ur hydraulic tank
if if comes out with swafe on

good luck in ur quest
if u want to pm me ill pass on my number then we can have a chat

regards wiggy

[shovel man]

have you checked main relief valves ? there are 2 in the main valve block, one for each track and excavator function, ie left track,
bucket and boom, right track, dipper and slew (may not be the exact combination) does the machine track ok when cold and loose power to the problem track when hot? if you are loosing power on the tracking it will also affect the digging functions, I had a similar
problem with a KX101 some years back replaced the main relief valve and al was ok, try swapping main relief valves first to see if that
moves problem to the other track it will be cheaper than a new pump.

shovel man

[vanwarren]

Once again thanks for your responses. The last thing I tried was to reverse the two flexible hoses (P1 and P2 outlet from pump) between the Hydraulic Pump and the inlet section of the Control Valve. The lazy track then moved from the left to the right of the machine. This makes me think that I have eliminated everything from the Control valve to the Track Motor and indicates that P1 in the hydraulic Pump is not working properly. Is this logical or am I oversimplifying. I would like to be sure before removing the pump.

[shovel man]

It sounds like you've tried every avenue if you have swapped hoses from the pumps and the problem has moved to the other side then
it seems like the pump is the problem, according to my info its a variable displacement pump with 2 outlets, might be worth
checking with your Kubota dealer if there is an explanation for loosing pressure on one outlet and not the other or the pump is just
knackered and needs replacing.

[bigkit]

Talk to heavy parts hydraulics in Rochdale they may be able to overhaul it. I understand they are very good.

[Mick-the-fitter]

thanks for the tips wiggy. I have made my own set of spanners following your suggestions, makes it a bit easier, but still a pain. By swapping left and right drive throughout the system I have narrowed it down to the hydraulic piston pump bolted to and driven by the engine. I am now having trouble locating a replacement unit. It is a Nachi Fujikoshi Variable Displacement Pump. Model: PVD-28-36L3DPS-8G-4117F. Can anyone out there help to locate this pump?

Hi mate,

How have you come down to it being the VDP? Does your dash 2 have reduction hubs on the drive motors or a gear train set up? Have you checked final drive oils? Or tested the distributor for leaks?

Mick

[vanwarren]

Hi Mick-The-Fitter. When I swapped the output hoses P1 and P2 on the PVD the problem switched from the left track to the right track. I took this to mean that the pressure produced at outlet P1 was low.

[Mick-the-fitter]

Hi Mick-The-Fitter. When I swapped the output hoses P1 and P2 on the PVD the problem switched from the left track to the right track. I took this to mean that the pressure produced at outlet P1 was low.

So you must be having problems with dipper and slew also! I see why your pointing the finger at the VDP.

Mick

[vanwarren]

Hi everyone
I decided after talking with a dealership that a repair kit for the pump might be the answer. Before purchasing however I decided to take the pump off and dismantle it. I saw little signs of wear and now with a bit more understanding of how the pump works can't understand why the pressure at outlet P1 should be much less than P2 as it is basically one pump supplying the two outlets via adjacent holes in the valve plate. I reassembled the pump and refitted it with no change to the machine performance, still a lazy left track. I am reluctant to buy a repair kit as I can see no reason for the low pressure at P1. Back to the drawing Board. Any suggestions gratefully received.

[Gerard]

is the left track lazy in both forward and reverse direction? if you take the rear cover off there is a case drain line on the motor. it may pay to warm the machine up remove and cap off the case drain hose and run another hose into a container preferably one you can use to measure quantity. do this with both track and compare what you find. there will be a set quantity in a technical manual.if there is a big difference the motor may be bypassing. make sure not to confuse it with the 2 speed travel hose. also lift the machine off the ground and test the travel speeds both high and low and compare them too.