charge pressure

[dusty-t]

Hey Guys. I took the b7200 to my local dealer because I thought the hydrostat was weak. I called today and they said that they checked the charge pressure it dumped to nothing. They say I need to rebuild the hydrostat. I don't know if he was planning on doing further testing because he said that he had'nt tested the high pressure yet. I am confused. HELP!!

 

[dusty-t]

Thanks for the reply Vic. I don't suppose there is a rebuild kit available. And yes I would rebuild it myself. Wengers in PA have a used one for a thousand bucks. But I don't need the tractor so I would rather take a crack at rebuilding it myself. But I need to Know I can get the parts I need before I start. Thanks again.

 

[eserv]

I would check the charge suction strainer before I committed to rebuilding the HST. Then overhaul or replace the charge pump. parts for the main part of the hst are very expensive and likely hard to get for your b7200

 

[dusty-t]

Thanks for the reply eserv. I gather the suction strainer is one of the screens that go through the hydro banjo fittings at the sides of the hydrostat unit. If so I have replaced both with new screens.

 

[eserv]

FYI A new HST to fit your tractor will sell for about 2300 Canadian. Kubota have one in stock at Markham.
Mount Forest Huh? My brother lives just north of Shelburne!

 

[ipz2222]

hst. Does that stand for hydrostatic transmission??

 

[eserv]

Yes, HST stands for Hydrostatic Transmission.

 

[eserv]

Hi Dusty-t
I didn't read your other thread until after i"d posted in this one so I didn't know you had changed the strainer.
The hst can be rebuilt easily enough, the problem is that kubota don't supply any parts for it anymore. That is not to say you cannot get parts from Kubota but you'll have to have a good partsman who is willing to take the time to source them from other models. probably it is rebuildable without any parts though!! if there is a good machine shop there who can resurface the valve plate (end cover in this case) and the rotating groups it might be all you need. This sealing surface gets scored and won't seal causing a "weak" hydro. This poor seal is where your charge pressure goes also.If it pulls smooth but lacks power and speed that is likely your problem. The check valves and high pressure relief valves, unless both of them are shot, will cause poor performance in either forward or reverse, but not both.
Could also be as easy as a broken spring in the pump or motor too.
You'll likely have to do it yourself though as few dealerships or repair shops will go inside one! You'll be surprised just how simple it is when you take it apart , just be as clean as you possibly can, these things hate dirt!!
Go for it!

 

[dusty-t]

Yup sounds like a plan. I will start tomorrow. I am really slow. 20 yrs worth of rheumatoid arthritis. But I do have a fair bit of sticktoitiveness. I have a wsm and a real good machine shop nearby. Thanks for the advice and if I bugger this up I won't blame anyone but me. And Yeah your brother is only about 30 min from me.

 

[dusty-t]

Hey Guys. Well it seems the project is on. Did some rippin and tearin tonight. Tomorrow I'll start pulling it apart.So far I have only stripped the the back.One question, in the fourth picture is a little black plastic thingy, is this a vent.

 

[dusty-t]

Well so much for that project. I was going to lie and say that other stuff broke and I didn't have time. And stuff did break down, but that wouldn't stop me from doing the Kubota. When I did the clutch, I had to do the clutch, it was busted and wouldn't move. And doing a clutch is something I am familiar with. T Since I cleaned the cooler it seems to have more power every time I drive it. So I put the wheels back on it and took it for a toot. That hill that it had trouble with. I can now stop half way down and back up it again. It is making the engine work quite a bit more than it did before. It has more power than it has ever had since I have owned it. The hydrostat is new territory for me. I guess I am wimping out. I don't want to tear a tractor that I really really like apart when it is working better than it ever has. Having said that am I going to do more damage by using it. I mean it has been like this for 4 years. And it is better now than it has ever been. I know it is not as powerfull as it could be. I guess what I am saying is that I am happy with it the way it is. AM I MAKING A MISTAKE ??. I don't worry this much about my kids.

 

[eserv]

Hi Dusty-t
Was the cooler plugged up or restricted? I guess if you are happy alls good, right? I don't think you'll cause any more damage running it like it is provided it doesn't overheat. If you can hold onto the cooler lines it is cool enough.
Ed

 

[dusty-t]

Hey eserv.Yeah the cooler was restricted. Quite a bit. I soaked it in gas for three days,then flushed it with tranny fluid umpteen times. But that was before I had the hydro tested.I only ran it for maybe 10 min before I took it to kubota to have it tested. And so far there does not seem to be much for heat. But the motor seems to be working harder now which means the hydro is working harder. I'll run it for a while tomorrow and keep an Eye on the hydro for heat. And thanks for helping, I appreciate it.

 

[dusty-t]

Ok Guys are you ready for this. I really didn't want tear that b7200 apart again.So I put wynns tranny flush through it. I figured if the hydro was pooched anyway so what did I have to lose. Well it will now dam near climb a wall in high range. Three point hitch don't work but I can climb a wall. Well actually the three point hitch does work when I'm climbing the wall. OK it was a small hill of about 45 degrees it wasn't a wall. And when I get back on the level the hitch won't go down. Any ideas anyone. If I wrecked the hydraulic pump I can deal with that. As long as my hydrostat is alright. And if I wrecked both then I will really feal like a goof. OK I started the tractor, both ports on the hydraulic block have plugs in them. If I turn the lever out the engine lugs down in a hurry. To me that means that the hydraulic pump is working. That leaves the 3ph valve which I tightened the bolts on yesterday. If I rev it up to about 2500 rpm the hitch will come up slowly.

 

[dusty-t]

Hey Vic And Mr K. maybe you can make a video about what not to do to your B7200.

 

[dusty-t]

Ok so it seems that using wynns tranny flush at least in the short term was a good idea. The hydrostat has a lot more power. The 3ph lever was just worn and sloppy and slipped off the fork, but the fork or the internal thingy that looks like an H was turned a bit so that didn't help. Anyway fixed it up stuck it back together and the 3ph works fine. Would someone please let me know of any information on the long term effects of using tranny flush. Thanks.

 

[eserv]

Hi Dusty-T
I don't think the tranny flush will do any harm........ Don't really understand why it did any good either!! Unless it made the oil a little heavier. I meant to ask you what oil you had in there? A hydrostat is about the only mechanical thing I've ever seen heal itself! Sometimes with a good oil change and new filters they will sort of wear themselves in over time. I wouldn't count on it but I have seen it happen.
Ed

 

[dusty-t]

Hey Ed thanks for the reply. I had dextron in it, flushed it and changed to hydraulic oil. It really surprised me when the power jumped like that.

 

[eserv]

I wouldn't recommend Dextron, I think it is too light for the kubota. That being said many are using it with good results. I recommend Kubota UDT ( of course I would, I work for the damn company!!) But It is a really good Universal Differential Transmission oil and many many times I've had customers call with problems and I ask them to change to UDT and the problem goes away!! especially true with powershift and hyd. shuttle tractors.
Ed

 

[dusty-t]

The engine actually gets warm now. In the last 4 years it hasn't had to work. But just warm not hot, hydrostat too. I figured I was in for a lot of time and a fair bit of cash to fix this. So far I am really really pleased. But I'm not counting my chickens yet!