Paying the orange tax. Kubota B7100D

[Scott Cee AKA 2drx4]

In the spirit of posting ALL of my crap 4wd stuff here, I present my Kubota B7100D.

This tractor is old, the serial number indicates a mid 1978 build date, but it's mostly decent. The hour meter doesn't work though, so ehhh. I bought it a few months ago, but I've been busy so I haven't had time to fix everything yet, but it does work as is. The first thing I did was change the fluids and looked everything over.

The front end loader uses its own hydraulic pump that's driven from an attachment off the front of the engine. There's also a pump that's driven from the timing case for the 3 point and any other auxiliary attachments. Here's what the oil in the loader looked like, and the screen (no filter).

Everything else wasn't too bad as far as the fluids went. Except when I went to drain the oil out of one of the front portals, and nothing came out. Because it was full of grease. Hmm, why would it be full of grease?

Because the portal housing is busted.

Luckily I managed to source a good used housing from the US. For the time being I put a zerk in place of the fill plug and just pumped more grease in. I am waiting on some seals and time to swap this out, it's probably been like that for 20 years so no sense getting urgent about it.

[Scott Cee AKA 2drx4]

This thing has been useful around the house. It isn't a toy. Okay, it's a toy, but it's still a real tractor.

The latest thing I got for it was a post hole digger/auger, often referred to as a PHD. I want to fence my place so this seemed logical versus paying somebody.

One of the known issues with these things is that they won't always bite in because there is no power down on a typical tractor 3 point hitch, they can only lift, so it's just the weight of the auger itself that's pushing down. The first hole I tried didn't want to go, so immediately decided to modify it instead of trying another hole.

I just welded on a piece of 1" sch 80 with a nut in the end, and then made a big T bolt that would act as a safety so whatever you put on there can't come off as easy. I threw some brake drums and rotors on it (not in the picture, I took them back off to paint it), and then it augured like crazy. Of course now the 3 point can't lift it back out, but that's most likely because the seals for the piston that lifts it are bypassing due to being 45 years old. So I ordered the seals for it. That will be a project for some point in a few days. Hopefully it works after that. Hopefully.

Anyways, I'll keep adding random things to this as long as there is some modicum of interest. I've been too busy trying to get this stuff sorted and things around the house to work on any off road 4x4 stuff recently. Content is content, eh?

[Junkjunk]

Love it

Sent from my SM-G991W using Tapatalk

[Scott Cee AKA 2drx4]

I needed to try to auger some more holes, so that meant I had to fix this.

The lift cylinder thinger is in the transmission top case, under the seat:

The "head" or cover, whatever you want to call it, comes off and then you can fish the piston out with a strong magnet:

It's an odd design, it's only single acting so the piston isn't attached to the rod:

The rod is covered in rust because of condensation, or water in the oil. I realized the shift boot is torn, probably why water gets in the oil, so I ordered a new one. The cool thing about this stuff is a lot of the parts are still available from the dealer, and not at bad prices, so you can order an OEM shift boot for a super old tractor for $12.

Piston, it's pretty scored up:

Again, since it's only single acting, the rod just gets pushed by it, so they basically built a ball socket into the end of it. This design definitely has downsides though.

[Scott Cee AKA 2drx4]

The bore is ugly, lots of scoring:

I went at it with a bunch of 400 grit and scotchbrite, but it's pretty difficult to make it much better. The seals for this are cheap ($10~), so I'm willing to just try it. Worst case I think I can pull the top case off and get it bored/sleeved/chromed or something as a repair. I'm not really sure what would be the standard repair. If the piston had a teflon/PTFE guide ring or two on it, I don't think there would have been any scoring damage.

Time to go augering:

So, does it work? Sort of. The 3 point no longer was falling on its own after doing this, so the new o-ring and bore cleanup was working much better, at least there wasn't static bypass. But, the auger attachment is still way too heavy, and has way too much leverage, so it still struggles badly to pull the auger out of the hole. With the 6" auger it wasn't terrible, I ran a bunch of post holes with it first, then switched to the 9" for some Sonotubes, and it really struggled. The auger design (these are from Princess Auto, you get what you pay for) is poor, I believe they would do a better job of ejecting the material if you bought better augers, or modded these ones up. I had to clean the 9" holes out by hand, it just wouldn't lift the material out. By the time I was done obviously the o-ring on the piston was getting beat up again, as the 3 point was back to falling (albeit very slowly) on its own again.

I think I'll have to decide if I want to just sell the auger attachment or try to mod things up more. The attachment for a Bobcat is a lot more money. I do have about 30-40 more post holes I want to do in the spring. Then after that I probably won't use it again for a while.

[Joe_the_ice_man]

Typically standard repair for a leaky cylinder (at least from a professional standpoint when shop rate is $150/hr+ and downtime is even more) is to throw a new parts in and call it done. That may change on the big, expensive ones. Kinda sucks that it's part of the transmission...

Honestly, I'd probably see about disabling that cylinder and adding an external double acting one on it's own valve if there was ports I could pull off.

This looks like good junk, I approve.

[Scott Cee AKA 2drx4]

Typically standard repair for a leaky cylinder (at least from a professional standpoint when shop rate is $150/hr+ and downtime is even more) is to throw a new parts in and call it done. That may change on the big, expensive ones. Kinda sucks that it's part of the transmission...

Honestly, I'd probably see about disabling that cylinder and adding an external double acting one on it's own valve if there was ports I could pull off.

It actually shows the top case as being available, $2868. As you say, if you're paying $150/hour that might be the way to go. Paying a machine shop to sleeve it probably would be less, but you would definitely need a quote to know for sure.

There is a kit to disable the 3 point cylinder and run an auxiliary valve, called a power diverter valve/kit. I'm not sure if it's available new, or if old stock exists, but that's basically what it's for. Typically it then works for a cylinder that goes in place of the top link on the 3 point, since there is some attachments that are better off being raised/tilted/etc that way than by the lower arms. It would be quite a bit of modification to the auger attachment to run it that way. There also was kits to plate over a bunch of the mount points on the top case, so you had another solid attachment point in the back, and that would possibly be easier to adapt for a cylinder mount location. Obviously you could just build that stuff, the kit was so people wouldn't have to do anything other than bolt it on. What I think is the better option is that the control valve for the loader can be replaced with one that has another (third) function and that can be used, and that's probably the way I'd go instead. Having the third function on the loader would allow you to do other largely useless things with it, such as installing a grapple, but it could be used to run any other cylinder that was required. But if you've gone that far you might be better off just buying a Vevor PTO hydraulic pump, a hydraulic motor, and then mounting the post hole auger's gearbox to the bucket (well, make a new FEL mount for it) and running it with that hydraulic motor. Then you have power up/down from the loader, and you have jam of the PTO driven hydraulic pump to turn it.

The neat thing about this stuff is you're only limited by time, money, creativity, and your willingness to die due to poor engineering choices. It's just like wheeling.

[Scott Cee AKA 2drx4]

Another idea I've had is to build a proper ROPS (roll bar) for it. There was one available when they sold them, but no farmer bought anything like that in the 70s, so they're unobtainium. If a guy did a decent enough job of building one, it could be used as a suitable attachment point for a cylinder to give you power up/down on the auger.

As a bonus you might not die if you rolled it.

[Joe_the_ice_man]

I didn't notice it ran off a PTO. Looks kinda sketch. Though maybe I'm just not a fan of PTOs.

What I think is the better option is that the control valve for the loader can be replaced with one that has another (third) function and that can be used, and that's probably the way I'd go instead. Having the third function on the loader would allow you to do other largely useless things with it, such as installing a grapple, but it could be used to run any other cylinder that was required. But if you've gone that far you might be better off just buying a Vevor PTO hydraulic pump, a hydraulic motor, and then mounting the post hole auger's gearbox to the bucket (well, make a new FEL mount for it) and running it with that hydraulic motor. Then you have power up/down from the loader, and you have jam of the PTO driven hydraulic pump to turn it.

That is the way they run them on skid steers and hoes (speaking of, I've been meaning to build one...) visibility becomes an issue on a tractor though. You could probably cheat and mount it offset to cheat the visibility issue.

Personally I would do that off an external PTO pump and run lines with quick connect fittings to both ends. Mostly just cause PTOs scare me.

As far as the cylinder in the transmission, I'd almost be tempted to very gently run a hone (as long as it's not a chromed bore) through it, its already broken, right? You just gotta make it stop chewing up seals, yeah?

[Scott Cee AKA 2drx4]

I didn't notice it ran off a PTO. Looks kinda sketch. Though maybe I'm just not a fan of PTOs.

What I think is the better option is that the control valve for the loader can be replaced with one that has another (third) function and that can be used, and that's probably the way I'd go instead. Having the third function on the loader would allow you to do other largely useless things with it, such as installing a grapple, but it could be used to run any other cylinder that was required. But if you've gone that far you might be better off just buying a Vevor PTO hydraulic pump, a hydraulic motor, and then mounting the post hole auger's gearbox to the bucket (well, make a new FEL mount for it) and running it with that hydraulic motor. Then you have power up/down from the loader, and you have jam of the PTO driven hydraulic pump to turn it.

That is the way they run them on skid steers and hoes (speaking of, I've been meaning to build one...) visibility becomes an issue on a tractor though. You could probably cheat and mount it offset to cheat the visibility issue.

Personally I would do that off an external PTO pump and run lines with quick connect fittings to both ends. Mostly just cause PTOs scare me.

As far as the cylinder in the transmission, I'd almost be tempted to very gently run a hone (as long as it's not a chromed bore) through it, its already broken, right? You just gotta make it stop chewing up seals, yeah?

I don't think visibility would be terrible as long as the bucket is off the loader, you can see over the hood decent on it because it's not big and you sit pretty high. But yeah, it's not like a skid steer where you'd be staring at the thing while it was augering. I guess a guy could make the mount offset like you say, hell you could pin it so you could move it to either side depending on if you needed more access. Hmm.

Honing it might work. I don't know how far I can go before I'm too out of spec and the o-ring will just extrude past the backup right. Of course a guy could look for a different backup ring and/or o-ring if it was a problem. Hmm. It's probably worth trying. I think if I did it I would be tempted to try to find some guide rings and cut grooves in the piston for one at least. I'm not sure how standard of a part they are, they use them a lot on aircraft stuff but nothing that big that I'm aware of. But if it worked it would probably then be a permanent repair since the bore shouldn't get scored again.

[Joe_the_ice_man]

Honing it might work. I don't know how far I can go before I'm too out of spec and the o-ring will just extrude past the backup right. Of course a guy could look for a different backup ring and/or o-ring if it was a problem. Hmm. It's probably worth trying. I think if I did it I would be tempted to try to find some guide rings and cut grooves in the piston for one at least. I'm not sure how standard of a part they are, they use them a lot on aircraft stuff but nothing that big that I'm aware of. But if it worked it would probably then be a permanent repair since the bore shouldn't get scored again.

Absolute worst case scenario, you could probably have a new piston made to your spec after you get all the roughness honed out. And still probably cheaper than getting a top cover.

Adding teflon guides is a really good idea. I'm sure you could get something from a hydraulic place, or even Greggs if you're lucky.

Otherwise, it's been a while since I've had a cylinder apart, but if I remember right the seals and guides usually bolt to then end of the piston. If you are willing to sacrifice some of your down travel, you could probably tap the piston and bolt a teflon disk to the pressure side of it. As for the other end, use a parting tool on a lathe and you may be able to cut a grove then make a teflon ring that installs like a piston ring.

[Joe_the_ice_man]

Second thought, that piston looks thin in the middle, maybe dont try and tap it