ClappedOutB7100
New member
Equipment
1978 Kubota B7100, FEL, rear ballast/ball hitch mounted on quick hitch
Hello all, new to the forum but have been browsing it a lot since me and my roommate picked up this old B7100. We paid $3,400 for the unit, which as far as I can tell is just about as cheap as they get on the open market - but we’re definitely getting what we paid for. For starters, we (and apparently the previous owner) thought it had 870 hours on it, but the paint on the 2 in the thousands place of the hour meter had worn off…
(Pic of day we bought it)
The first issue was the loader - it didn’t work at all when we picked it up. The owner offered to turn his torpedo heater on and blast the tractor for a couple minutes to get it working… not a good sign. The tractor ran ok otherwise, so I decided it was worth buying if that’s all we needed to fix. Being new to tractors (but very experienced with other mechanical stuff) we threw a lot of parts at it before actually finding the problem.
The first thing we found was water contamination in the oil and ice in the loader reservoir screen, which explains why PO offered to use his torpedo heater. We tried to flush the system, but found the fluid was still being aerated and possibly water contaminated. Operation of the loader was extremely slow and inconsistent.
(pic of milky hydraulic oil flush from the first day we had the tractor)
Since the soft lines were also in really bad shape, I wound up replacing them first since they’re cheap enough. After we replaced them, the added pressure burst a hard line, so we had another made at a local shop. Still finding the fluid was becoming aerated and/or water contaminated, I decided it was probably bad seals in the cylinders letting water in. While resealing the cylinders was a ton of fun, it unfortunately didn't make much of a difference. It had to be the valve or the pump. At this point, I was pretty determined, so for good measure I replaced both...
(pic showing off the gross old painted soft lines and original hydraulics)
I wanted to rebuild the original Cessna units, but they were in pretty bad shape. The valve had weak springs and corrosion from all the water in the fluid, and the pump was so worn that a copper plate within had formed pinholes (explaining the aerated fluid). Doesn’t help that any parts/seals for the FEL pump are NLA. So, I got to researching to see what it would take to replace the worn out Cessna pieces with generic aftermarket parts.
For the valve, I had to learn a lot about hydraulic thread types. ORB, SAE, NPT, BSPT… my head was spinning. At first we ordered a generic valve that used BSPT, and it took me a couple of hours of research to figure out that it would be easier to just get an SAE valve. I chose one with a third function in case we want to add a thumb/grapple to the bucket later on. After getting the right fittings, installing the valve was as simple as finding some hardware and fabbing a bracket. However, this still didn’t improve the loader performance the way I wanted, so I knew I would have to replace the pump after all.
(pic of new valve vs. old unit)
I went with a Chief brand 14cc pump (factory pump is 8.2cc!) which I was unsure about using due to the added load on the engine - there was also a matter of shaft size difference, the original Cessna pump’s shaft is 9/16” while the Chief’s is 5/8”. Fitment was also a concern since there didn’t seem to be a ton of space between the loader frame and the FEL pump bracket.
After a LOT of searching and wasted time machining the original coupler sprocket to fit the new pump, I found that Surplus Center sold the “custom” sprocket I was looking for at the low price of $13. That made me feel pretty dumb. So, some new chains and a $13 sprocket later, I had everything I needed for the project. All I had to do was fab up some brackets to mount the pump using the original threaded holes on the tractor frame and we were good to go! The fitment is pretty tight, but it’s just about perfect.
(pic of new pump vs old unit)
Now, having replaced essentially the entire loader hydraulic system aside from 3 hardlines and the reservoir, I was ready to test it. Man, does this thing move now! Yes, you can stall out the engine if the RPMs are too low and you’re asking too much of the loader, but the performance is incredible for this size tractor. I have some concerns about head generated from the new pump and possibly starving the pump with the size of the factory reservoir, but in around 10 hours of operation so far, it’s worked flawlessly!
(pic of it all sorted!)
All-in, think it was about a $600 project to get a ~60% increase in pump displacement, add capability for a 3rd function, and refresh all the lines/hardware/fluid. Goes without saying that we could definitely get ourselves into trouble with the additional hydraulic power, but that’s sort of the fun of it, right?
Seal Kit: Kubota 70050-00123
Pump: Chief Group 2 Gear Pump (2PG) - 0.85 CID (14CC), 5/8" Key Shaft, SAE-A 2B Mount, SAE-12/10 Ports, CCW Rotation
Valve: Hydraulic Tractor Loader Control Valve 3 spool, 11GPM SAE Ports Double Acting Hydraulic Directional Flow Control Valve w/Joystick for Log Splitters, Tractors Loaders
(Pic of day we bought it)
The first issue was the loader - it didn’t work at all when we picked it up. The owner offered to turn his torpedo heater on and blast the tractor for a couple minutes to get it working… not a good sign. The tractor ran ok otherwise, so I decided it was worth buying if that’s all we needed to fix. Being new to tractors (but very experienced with other mechanical stuff) we threw a lot of parts at it before actually finding the problem.
The first thing we found was water contamination in the oil and ice in the loader reservoir screen, which explains why PO offered to use his torpedo heater. We tried to flush the system, but found the fluid was still being aerated and possibly water contaminated. Operation of the loader was extremely slow and inconsistent.
(pic of milky hydraulic oil flush from the first day we had the tractor)
Since the soft lines were also in really bad shape, I wound up replacing them first since they’re cheap enough. After we replaced them, the added pressure burst a hard line, so we had another made at a local shop. Still finding the fluid was becoming aerated and/or water contaminated, I decided it was probably bad seals in the cylinders letting water in. While resealing the cylinders was a ton of fun, it unfortunately didn't make much of a difference. It had to be the valve or the pump. At this point, I was pretty determined, so for good measure I replaced both...
(pic showing off the gross old painted soft lines and original hydraulics)
I wanted to rebuild the original Cessna units, but they were in pretty bad shape. The valve had weak springs and corrosion from all the water in the fluid, and the pump was so worn that a copper plate within had formed pinholes (explaining the aerated fluid). Doesn’t help that any parts/seals for the FEL pump are NLA. So, I got to researching to see what it would take to replace the worn out Cessna pieces with generic aftermarket parts.
For the valve, I had to learn a lot about hydraulic thread types. ORB, SAE, NPT, BSPT… my head was spinning. At first we ordered a generic valve that used BSPT, and it took me a couple of hours of research to figure out that it would be easier to just get an SAE valve. I chose one with a third function in case we want to add a thumb/grapple to the bucket later on. After getting the right fittings, installing the valve was as simple as finding some hardware and fabbing a bracket. However, this still didn’t improve the loader performance the way I wanted, so I knew I would have to replace the pump after all.
(pic of new valve vs. old unit)
I went with a Chief brand 14cc pump (factory pump is 8.2cc!) which I was unsure about using due to the added load on the engine - there was also a matter of shaft size difference, the original Cessna pump’s shaft is 9/16” while the Chief’s is 5/8”. Fitment was also a concern since there didn’t seem to be a ton of space between the loader frame and the FEL pump bracket.
After a LOT of searching and wasted time machining the original coupler sprocket to fit the new pump, I found that Surplus Center sold the “custom” sprocket I was looking for at the low price of $13. That made me feel pretty dumb. So, some new chains and a $13 sprocket later, I had everything I needed for the project. All I had to do was fab up some brackets to mount the pump using the original threaded holes on the tractor frame and we were good to go! The fitment is pretty tight, but it’s just about perfect.
(pic of new pump vs old unit)
Now, having replaced essentially the entire loader hydraulic system aside from 3 hardlines and the reservoir, I was ready to test it. Man, does this thing move now! Yes, you can stall out the engine if the RPMs are too low and you’re asking too much of the loader, but the performance is incredible for this size tractor. I have some concerns about head generated from the new pump and possibly starving the pump with the size of the factory reservoir, but in around 10 hours of operation so far, it’s worked flawlessly!
(pic of it all sorted!)
All-in, think it was about a $600 project to get a ~60% increase in pump displacement, add capability for a 3rd function, and refresh all the lines/hardware/fluid. Goes without saying that we could definitely get ourselves into trouble with the additional hydraulic power, but that’s sort of the fun of it, right?
Seal Kit: Kubota 70050-00123
Pump: Chief Group 2 Gear Pump (2PG) - 0.85 CID (14CC), 5/8" Key Shaft, SAE-A 2B Mount, SAE-12/10 Ports, CCW Rotation
Valve: Hydraulic Tractor Loader Control Valve 3 spool, 11GPM SAE Ports Double Acting Hydraulic Directional Flow Control Valve w/Joystick for Log Splitters, Tractors Loaders
