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Kubota B4690 Backhoe Attachment to JD 950

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BigRed
Join Date: Jul 2003
Posts: 6 Nevada
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2003-01-14          47505


I have a JD 950 with a Blackhawk 7-1/2' backhoe w/subframe. I am fairly inexperienced with the smaller tractors and attachments. We bought a piece of property that is forested and I wanted a tractor for general cleanup and work around the place. This is my concern.
The Blackhawk backhoe with seperate pump (PTO driven) does not seem to have any power. When I lift the back of the tractor to position myself or push myself forward while seated on the hoe, the valve bypass squeels and I do not have enough power to push the tractor ahead (level grd). I have ran the larger Case 580's. Am I asking too much? Can the bypass valves be adjusted to provide additional pressure.
I can purchase a Kubota B4690 3ph attachment very reasonable. The pump on this unit is also pto driven and almost 2x the size of my Blackhawk pump. The owner says the B4590 is powerful enough to move the JD950 around. What should I be aware of? Subframe vs 3ph. What about matching the B4690 to the back of the JD950? We live in Reno area and my tractor is in Oregon so its difficult to compare. Any help would be "greatly" appreciated. I had also posted that I was looking for a p/s unit for the 950. If anyone has any input as far as a used unit goes, that would be appreciated as well.
Please feel free to send any coments to my e-mail.
Thank you!




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Kubota B4690 Backhoe Attachment to JD 950

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-01-15          47532


I don't know if you have identified the relief valve on the hoe. Mine is adjustable and I think most are. It's a screw adjustment under a cap nut on the valve's inlet section.

It's best to make adjustments with a gauge rather than simply increasing it to see if the hoe seems to work better. Gauges are pretty cheap. Hoe specs should be checked for relief pressure settings but 2,000 - 2,200 lbs. are typical pressures for small equipment.

The test procedure for my hoe is to remove a stabilizer hoes, connect it to the gauge and then operate the stabilizer valve, take readings and make adjustments. If the pressure is low and comes up when the relief valve is adjusted then the pump and spooling valve probably are OK and relief valve is the problem. However, the hoe may still be weak due to valve or cylinder leaks in other circuits.

Hydraulic pumps in decent condition can withstand pressures far in excess of working system pressures. Unless there's a lot of leakage in hydraulic components or internal pump leakage a bigger pump (in terms of gpm rating) would make the hoe work faster but wouldn't give it more power.

I'd compare the gpm ratings of the pumps rather than their physical size. I'd also compare reservoir size. Reservoir size should be around 2.5 times the gpm rating to give adequate heat dissipation for heavy work. It does sound like heavy work is anticipated if the hoe is going to move the tractor around so heat could be an issue. For heavy work, a sub-frame hoe in general is preferable to a 3ph hoe. There's a bunch of discussion on the subject in the archives.
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Kubota B4690 Backhoe Attachment to JD 950

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DRankin
Join Date: Jan 2000
Posts: 5116 Northern Nevada
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2003-01-15          47539


Be real careful with 3ph mounted hoes on small tractors. They can create some catastrophic problems. I would try to adjust what you have or look into a new pto hydro-pump with more capacity.
BTW you are not signed in so your E-Mail does not pop up. ....


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Kubota B4690 Backhoe Attachment to JD 950

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BigRed
Join Date: Jul 2003
Posts: 6 Nevada
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2003-01-21          47921


I wanted to take a moment to thank Tom G and Mark H. for their imput. I must appologize for the length of time it has taken for me to get back, however I somehow managed to trash our computer and am now just getting things back on-line.
Tom, I appreciate the information regarding the pressure check. Could you suggest the type of guage or a part number. I might have a better chance of picking one up here locally better than in a smaller town.
You mentioned a working pressure of between 2000/2200psi. Are all the valves set at the same settings? What does the adjustment look like?
I plan on going up to our property next month and want to check this out as well as any other suggestions you might have.
Thank you ahead of time for your help! ....


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Kubota B4690 Backhoe Attachment to JD 950

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-01-22          47935


Just coming off a computer problem myself. It was a problem of my own making though.

Not all valves are adjusted the same and there should be a pressure spec available from the hoe manufacture. My 2,000-2,200 lbs. were only typical pressures and an actual spec for the hoe should be used. If you were running from tractor hydraulics, I'd keep in mind that no matter what the hoe spec is or adjustment on the hoe valve, the pressure wouldn't go higher than the adjustment on the tractor's system relief valve.

Hydraulic pressure gauges are pretty universal things (at least in theory because I have to buy one myself this spring). There are cheap gauges available from Northern Tool and I imagine other on-line tool suppliers and probably from box stores as well that should be adequate. Ones from tractor dealers and pro hydraulic shops are expensive. A 0 - 3,000-scale gauge should work pretty well. Hydraulic gauges are fluid filled for better damping, b ut even old welding bottle gauges work OK.

You just need the gauge and a fitting to connect it into the system. It would be good to get fittings from a hydraulic shop or tractor dealer to make sure they are actually rated for hydraulic use. In addition, taking a hose to a shop will positively identify which fitting is needed. It might be a bit tricky to be sure of getting the right threads unless the manufacture can be contacted or a hose can be removed and taken to a shop.

I forgot to add that taking a pressure reading blocks the system and forces the relief valve to open. The control valve is held open only long enough to take the reading--otherwise the oil over-heats.
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Kubota B4690 Backhoe Attachment to JD 950

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Captain B
Join Date: Feb 2002
Posts: 53 West central New Hampshire
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2003-01-22          47950


BigRed--I had an Arps 7 (7.5') with PTO pump on my JD850 for five years. Your problem occurrs only when you try to lift the back of the tractor to position yourself or move forward as you do with the big guys! You are correct to suspect that you are asking too much. I wouldn't change the relief valve setting even if you can. Get a bigger hoe or resign yourself to hopping down every 10 to 20 minutes and moving around the conventional way. It's slower but darn good exercise. You'll sleep better from the workout and the peace of mind of not being between tractor and hoe if the subframe lets go. ....


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Kubota B4690 Backhoe Attachment to JD 950

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BigRed
Join Date: Jul 2003
Posts: 6 Nevada
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2003-02-01          48529


Thanks for the post. We all need exercise in some form or the other.
Working in and around trees, side-hills precluded me from purchasing a larger hoe. I am quite happy with what I have and only was looking for a way, if one was available, to improve upon the current situation.
Having said this, has anyone hooked the hydraulics directly to the hoe with quick-disconnects, thus bypassing the little pto driven pump?
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Kubota B4690 Backhoe Attachment to JD 950

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-02-02          48534


I run my 6' hoe from 6.3 gpm tractor hydraulics. The speed is generally OK even if I do find myself wishing that full buckets would come out of deep excavations a bit faster.

I don't know how the tractor and PTO pump rated flows compare. Usually people use pto pumps because the flows are greater than from tractor hydraulics. That may not be true with a self-contained small hoe and pump. It certainly is feasible to run a hoe from the tractor by adding quick-connects. A larger tractor pump would give more speed but the same power--assuming that the hoe's relief valve is set lower than the tractor's relief.

I run my hoe from a 3rd valve controlled outlet on my loader valve although most people splice the hoe into a loader's power-beyond line. However, you do have to be careful not to connect it backwards or a lot of damage can be done in a short time. You also have to be certain that the hoe valve is rated for power-beyond applications or run the risk that the hoe will never be operated at the same time the 3ph is in lift mode. High pressures from heavy loads on the 3ph can damage an upstream valve. My hoe valve may be rated for PB applications, but my connection avoids the problem. Return oil from the hoe flows through the loader valve's TANK line directly to the sump rather than on to the 3ph. Not all loader valves have a TANK line.
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Kubota B4690 Backhoe Attachment to JD 950

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BigRed
Join Date: Jul 2003
Posts: 6 Nevada
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2003-02-02          48542


Tom, it does appear from the number of posts and your overall knowledge of tractors/hydraulics,that you are very capable, as I am sure others are, when it comes to offering advise.
I am going to buy a guage and check the current pump's pressure. If adequate I will then check on adjustment of the valves. I am also going to check on a 3rd valve set up like yours and see if the tractor hydraulics makes a difference.
If the B4690 can not be used, I will make the unit available at a very reasonable price!
To all, have a great day!!! ....


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Kubota B4690 Backhoe Attachment to JD 950

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2003-02-03          48576


Thanks for the kind words. I wouldn't confuse quality and quality though. I made most of the posts because I was learning something, and many of them would be a lot shorter if I wasn't.

I should say that my hookup is sort of a haywire setup and a PB kit would be preferred. Running the PB flow through a SCV probably cuts the flow a bit and may contribute to heating. The PB flow also probably erodes the SCV orifices a bit and will take some life off the valve.

However, I haven't had any of those problems. My use of the hoe is occasional and light. I don't worry much about the loader valve failing because I'd like to replace it with a 4- control valve model and one with a fast dump feature for the bucket circuit. My hookup does avoid the PB issue if I didn't know whether the hoe valve was PB rated or not.
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