Backhoe Quick Coupler for Kubota B21

[downsizingnow48]

I have been thinking of making a quick coupler for my B21 for a couple years, but the project never quite makes it to the top of the list. Then the other day I read a post by LD1, making the point that if the attachment you want is commercially available, almost always it makes sense to buy and get on with the job, rather than build. Since I had been thinking of making this thing for such a long time, that really struck home.

So I did some looking around. Turns out that BXpanded makes a quick coupler for the Kubota B75/76/77 backhoes. From my hydraulic thumb build, I figured out that the buckets and pins for those backhoes are interchangeable with the B21 backhoe. So even though BXpanded does not list the B21, I went ahead and ordered one.

It works fine. I had to sand off their thick aluminum factory coating because it made the bottom part of the coupler too wide to fit easily between the Kubota bucket ears (another poster had the same problem on his B76 bucket). I repainted it with Kubota excavator black, which I like better than the aluminum anyway.

Especially with the thumb, changing between buckets was a chore that I did not look forward to. The BXpanded coupler makes the process much easier.

I knew from my own planning that the quick coupler would change the relationship between the thumb and bucket. Instead of closing completely at the teeth, there is a gap. I don't think it will make any difference in use but will have to work with it for a while to be sure.

 

[Tompet]

I bought the same q/a for my bh77 and it certainly makes swapping ripper to bucket easier. It does change geometry and increases gap between thumb teeth and bucket teeth, as you mentioned, which hasn't been much of an issue. It does make bucket "sloppier" on pins. How is bucket slop with q/a coupler on your machine?

One other thing is it seems to have limited full bucket rotation as far as a true 180 degree opening, which is a little more of a practical limitation in day to day use. Have you noticed that change?

Overall, in time savings switching out the two seems worth it.

 

[downsizingnow48]

I noticed the BXpanded pins went in easier than Kubota pins. When I measured them, the chrome BXpanded pins are about 24.5 mm vs the Kubota pins at 25mm. That will contribute to bucket slop. I have a bunch of Kubota pins around so am using them. I haven't measured the BXpanded coupler bushings, will do so next time I take the coupler off.

Just measured between the bucket ears. On the Kubota digging buckets it is 4 7/8" plus a bit. On the coupler the corresponding measurement is 4 15/16. That will also contribute to slop.


I don't see any difference in range of rotation due to the coupler alone. Putting on the stump ripper, and a demolition bucket I made, there is a full range of rotation. It is only with the Kubota digging buckets that there is some interference between the bucket and the back of the thumb. That keeps the bucket an inch or two short of full close.