charge pressure

[dusty-t]

Ya thanks Vic, I had it apart a couple years ago to put a new relief valve in. I had an awfull time getting the control arm and regulator arm into that fork thingy. Turned out when I put it together the fork thingy was twisted a bit and the control arm fell out. I'm either going to start using pictures to explain what I mean . Either that or start learning the names of thingys. Anyway I figured out the trick to make it go together easier and right.Please for the love of God do not ask me how I did it now!

 

[sdcassel]

B7200 HST Charge Pressure

What was the end result; were you able to rebuild your HST? I have the same problem; the transmission works fine except on a grade or really loaded.

The dealer tested and the charge pressure is zero. The screens are clean, so they say the only option is a new HST unit for $1600 (parts alone). I can't find a machine shop willing to look at it, since Kubota doesn't show any serviceable parts.

I've got too much time and $$ invested to give up now!

 

[sdcassel]

Is there any way to test a used HST that was pulled from another B7200?

 

[sdcassel]

Can an HST from a B7200 be rebuilt?

 

[sdcassel]

We pulled the charge pump off the front of the HST. The rotor was shattered and the key sheared. Now I'm looking for used parts to avoid the $1600 price tag for the entire HST.

 

[sdcassel]

I found a used B7200 HST to pull the charge pump rotor from. I know of one other person that the only thing wrong with their HST was a shattered charge pump rotor (and probably sheared key). I'm thinking that when I get the intact rotor I'll see if a machinist can duplicate it. How common is it for that rotor to fail, and what might cause it? My mechanic thinks someone may have serviced it before and reassembled it incorrectly; the key may have sheared and scrambled the rotor.

 

[dusty-t]

The end result was that the hydro was much improved. I don't think it is as good as when it was new but it was a lot better than it had been. You must understand, this tractor had very poor service before I got it. I think it was just 25 or so years of junk build up in the system. I flushed the system again, changed filter, checked screens and put kubota fluid in it. I sold to it to a guy local to me about a month ago, and no bad reports so far. And yes I explained the history to him. Good luck with yours. I have been so busy lately I haven't been on here much. I have a B8200 that I need to get at too. Keep us posted.

 

[sdcassel]

The charge pump inner impeller (gerotor) was not reproducible, according to the machinist. I'm waiting to hear back from an outfit in Tupelo, Mississippi that rebuilds HSTs to see if they can get the part for the charge pump, which is manufactured by Kayaba. In the meantime, I used the impeller out of the used HST, and my transmission works good as new! I split the salvage HST and transmission, and will re-sell them on Craigslist to try to recoup some of the $450 I had to pay for the salvaged unit, just for that one little part! But that beat the $1600 for a new HST. I will make sure the buyer of the HST(E) knows the inner impeller is missing.

 

[eserv]

Hi
On the f series tractors you can direct the return oil from the hydraulic lift into the charge curcuit to get a machine running with a failed charge pump ( not all that uncommon a failure either! I think it might be moisture in the oil freezing and locking the pump which breaks when you then try to start the tractor) I have never tryed using return oil on a b series, it would be a lot harder to do because of the design of the hyd. system. Using a little enginuity almost any pump could be put into service to act as a charge pump even a power steering pump driven off the fan belt! Now we ARE getting a little redneck! It would get an otherwise useless tractor functional again considering Kubota only supplies expensive new Hydro assemblies for them
Ed Service

 

[dusty-t]

Hey Guys, This thread just keeps coming up with more info. Someone has to get into fixing these old hydrostat units. $1500 for the hydrostat unit is a lot less than I was quoted.They don't seem to be that complicated a unit, yet most of the service techs I talk to have either a blank look or fear in their eyes when discussing repairing them. And this isn't just kubota, it is any make of hydrostat. Sdcassel and eserve you guys seem to be ahead of the game on this. Sdcassel you are the first guy on here that I have seen who actually had the moxy to even rip the thing apart let alone fixing it. And Eserve you sound like you have done the same more than once. Thanks for the replies guys, it really gets a guy to thinking.

 

[sdcassel]

I have half a mind to find a machinist that will reproduce the impellers for the HST charge pumps! No telling how many discarded HSTs are out there that only need those charge pump parts replaced! Seems like a guy could make a living off saving others like me some serious $$$!

 

[brokersdad]

Funny I came across this post because I posted here a couple weeks ago how i thought my L3010 was lame for power. I was talking to the service rep at the local dealership and he told me that in the L3130 I believe they found some to have low pressure in the hydostatic, but the one in particular he told me about, he claimed they made an adjustment and it made a huge improvment . He said it was about an hour and a half job to check it over but he highly doubted I had an issue there. As that post i made then stated, I think it was me anyway not used to running it. Anyway, what he said to me, anyone know if adjustments are possible , just so i know in the future.

 

[dusty-t]

Hi Brokersdad, There are several different relief valves to set the pressures in different parts of the hydrostatic transmission but unless you have the proper equipment and know how its not some thing you want to try at home. There is a setting for the hydro pedal so that it centres properly and doesn't creep, and there is a dampener so that you don't smack your face off of the steering wheel when you take your foot off the pedal. Dusty

 

[brokersdad]

yea Dusty, not something i would ever attempt, just was curious if it was something that could be checked if a problem ever arises

 

[Greg]

Hi Brokersdad, There are several different relief valves to set the pressures in different parts of the hydrostatic transmission but unless you have the proper equipment and know how its not some thing you want to try at home. There is a setting for the hydro pedal so that it centres properly and doesn't creep, and there is a dampener so that you don't smack your face off of the steering wheel when you take your foot off the pedal. Dusty

Ahh, good info. I nearly slammed my face into the steering wheel this week when testing my my loader hook up. Makes sense that there is an adjustment for this.