Kubota G1900 Hydrostat Problem Repaired

[sixbales]

I've noticed a number of G1900 owners complaining that there mower was slow to get moving - took a while to get the hydrostat warmed up and moving. Reverse was slower to respond than forward. I had this same problem. One observation I made - when the hydrostat was acting up, the fluid on the dipstick was creamy/milky (full of air - not condensation).

Just wanted you to know that I repaired my Kubota G1900 hydrostat today, and it works great! I removed the seat, rear cover, and fuel tank to get to the hydrostat. On the top of the hydrostat, I noticed a very small hydraulic leak at the suction connection. The connection is just an o-ring in a groove in the pipe, pushed into a bore in the hydrostat. Actually a poor design - but it worked fine for 10 years

Drained the fluid, removed the pipe, and replaced 3 o-rings on it. It was sucking air through this leaking connection on top of the hydrostat. Put in new fluid and filter and away we went. Very responsive - like new.

This repair made my day!

 

[john_bud]

Great post and welcome to TBN!

Can you post a picture of the pipe fix and o-ring sizes? That may help out even more.



jb

 

[sixbales]

I cannot provide a picture of the tube and o-rings, but I can provide part numbers - as follows:

Tube - P/N 66101-36410
upper o-ring (1) - P/N 04811-00110
lower o-rings (2) - P/N 04811-10300

Follow-up to my original post - my G1900 hydrostat is still performing very well!

Additional comments regarding my original post:

1) The dipstick I was referring to (when checking for air in the hydraulic fluid) in my original note was the transmission dipstick at the rear of the mower. Very simple check to make.

2) I did not replace the tube, just the o-rings. Perhaps I should have replaced the tube as well?? The tube did not seat very deep into the hydrostat bore. It may be warped from 10 years (1500 hrs) of service, or it may have been manufactured with this configuration. I did give it a few raps with a hammer on a piece of wood to seat it a bit deeper into the hydrostat. and I put some silicone sealant at the top of the bore.

 

[sixbales]

Attached is a picture which includes the hydrostat tube I was referring to. The suction tube is on the right hand side of the schematic. It draws fluid through the suction screen at the bottom of the reservoir and delivers the fluid to a bore on the top of the hydrostat.

 

[bjmsam]

My G1900S (over 2000 hours with only regular maintenance) has been dripping hydraulic fluid from around the filter assembly for a year or so, and today it finally let loose (I happened to notice a trail after crossing the driveway). The leak appears to be from the bottom of pipe 010 in the diagram below, so the repair will presumably involve replacing O-ring 020 (and perhaps O-ring 060 for pipe 050 while I'm at it). Will removing the seat, rear cover, and fuel tank as described above provide the required access, or would it be wise to leave this one to a pro? Advice appreciated!

66101-36430 010 PIPE HST
04811-10090 020 O RING
66101-36444 050 PIPE HST
04811-10090 060 O RING

 

[bjmsam]

I gave it a shot this afternoon and things went smoothly. Pipe 010 was readily accessible after removing only the seat and rear cover, but pipe 050 would have been much trickier without removing the tank, so I held off on that one. I unscrewed the compression fitting, pulled out pipe 010, replaced broken O-ring 020, reinstalled the pipe, replaced the filter, topped off the fluid and found no leaks. Success!

I found several hydraulic lines connected to the control module that I don't see in the parts catalog. One was capped off...

 

[TDCornwell]

I wanted to weigh I on this old thread with a hearty *thank you*! My old G1900 was having the same symptoms: hydro not wanting to move much, reverse worse than forward. I took the rear panel off, cleaned the hydro unit off, and lo & behold, what appears to be the main line feeding the pump had a gap where the tube went in the top of the unit. It was clearly not sealed very well, so I cleaned it up & filled the gap with RTV, hoping this would help. It did! It is a temporary fix, and I will replace the o-ring when the weather gets warmer here.
Thanks for the info, and a big thanks to TractorByNet!