Rockhound mulcher

1willy

New member

Equipment
kubotaL35
Oct 2, 2011
4
0
1
ca
Hi I'm new to forums so I hope I'm doing this right, I have a new kubota kx057-4 90 hours with a rockhound mulcher the problem is Iv been through 3 hydraulic motors in 15 hours, after several hours the mulcher just get lethargic. Rockhound has replaced the motors every time and the last motor they added a case drain, every motor last about three to four hours, I've been stuck on the same job going on a month now with all the back and forth and waiting, I can't work on these things to much or I'll void my warranty, any ideas? Thanks
 

UpNorthMI

Well-known member
Lifetime Member

Equipment
L3200, L3901, MX5800, SVL75-2, KX040
May 12, 2020
850
568
93
Up North, MI
I run a new KX040. Are you using Aux 1? GPM is variable, there are several operation modes. I use hydraulic motor with case drain on disk mulcher on compact track loader, it runs well.

sounds as if rockhound has now upgraded the motor, do you know the spec of the motor fitted, I believe your Aux 1 circuit is giving 18 GPM. Hydraulic motor needs to match your machine hydraulic output.

are you using the mulcher within its capacity or are you trying to do too much work with it?
 

1willy

New member

Equipment
kubotaL35
Oct 2, 2011
4
0
1
ca
I run a new KX040. Are you using Aux 1? GPM is variable, there are several operation modes. I use hydraulic motor with case drain on disk mulcher on compact track loader, it runs well.

sounds as if rockhound has now upgraded the motor, do you know the spec of the motor fitted, I believe your Aux 1 circuit is giving 18 GPM. Hydraulic motor needs to match your machine hydraulic output.

are you using the mulcher within its capacity or are you trying to do too much work with it?
Hi Im running on aux mulcher #3 apparently this mulcher head is matched to my machine and I'm supposed to be running full power on setting and full throttle,I'm not quite sure gpm it works great for the first few hours, they claim 6" trees and at first few hours it goes right through them like butter but after about three hours it barely cuts tall grass. Apparently the kubota dealer has sold around 50 setups like mine with no complaints.
 

greenacresnorth

Active member

Equipment
L2501,BH77
Feb 18, 2018
175
28
28
38
Morganton,NC
are they telling you what is failing on the motor? im assuming your running the FX26? if so your well inside the max and min pressure and flow requirements. im not 100% familiar with the Kubota mini ex machines but I know with Cat you have to set a valve from hammer to motor mode. with hammer mode it will only flow one direction and it directs all fluid returned through the oil cooler. if temps are not in check you may want to try hammer mode. Im wondering if you have excessive return side back pressure? have they T'ed into the supply and return and checked pressures while running under a load? have they checked your hyd filters for trash? is the dealer doing a fluid change and flush after the motors fail? last question, what are we running for fluid? what is Rockhound spec'ing for a fluid?

in my experience depending what type of motor you are dealing with, heat and excessive return backpressure kills motors more than anything else, keeping in mind max pressures and the correct fluid are used.

saying that, I have issues every fall and winter with my Cranes blowing up pumps when the temps fall. Manitowoc specs a AW32 oil for the HYD system, people for some reason want to run AW46 and because of cold viscosity it grenades the cylinder walls on the pump. not saying thats the issue but if they are running a oil too thin, we could be having a lack of fluid film thickness and getting metal on metal contact after a short run time over time taking the motor out. excessive heat can do the same thing.
 

1willy

New member

Equipment
kubotaL35
Oct 2, 2011
4
0
1
ca
Fx26,They have not really told me what happened inside the motor, the kubota is on one way setting They're just replacing the motor and sending it back to me, the first time they thought it was the check valve on the machine so they sent a new motor with an inline check valve and that failed then they took the attachment back to the manufacturer and replaced the motor and put on a case drain and the kubota mechanic brought the mulcher to me and checked the pressures with their pressure checker (I'm not a mechanic) and said that it's at the manufacturer specified pressures they have not said anything about the oil viscosity or checked the filters it's running the oil that came with the machine, I just assumed that they would run the proper oil and check whatever they need to check because they're paying for all this stuff and those motors can't be cheap, thanks
 

1willy

New member

Equipment
kubotaL35
Oct 2, 2011
4
0
1
ca
Fx26,They have not really told me what happened inside the motor, the kubota is on one way setting They're just replacing the motor and sending it back to me, the first time they thought it was the check valve on the machine so they sent a new motor with an inline check valve and that failed then they took the attachment back to the manufacturer and replaced the motor and put on a case drain and the kubota mechanic brought the mulcher to me and checked the pressures with their pressure checker (I'm not a mechanic) and said that it's at the manufacturer specified pressures they have not said anything about the oil viscosity or checked the filters it's running the oil that came with the machine, I just assumed that they would run the proper oil and check whatever they need to check because they're paying for all this stuff and those motors can't be cheap, thanks
The kubota dealer told me this morning that they're giving me a full refund on the mulcher so any recommendations on a replacement? Thanks