Backhoe Backhoe Piston Hitting Fitting (BH75)

[TBNDave]

Having an issue when fully extending my backhoe bucket piston (fully curling the bucket inward). The piston draws too tight to the arm and hits a hydraulic connection. BH75 backhoe on a Kubota L3400.

Recently greased and pressure seems okay (hydraulic oil gauge reads favorably and the FEL works fine). I've put about a hundred hours on this backhoe and this is the first time I've had this issue.

Any ideas?

 

[cglaser104]

Having an issue when fully extending my backhoe bucket piston (fully curling the bucket inward). The piston draws too tight to the arm and hits a hydraulic connection. BH75 backhoe on a Kubota L3400.

Recently greased and pressure seems okay (hydraulic oil gauge reads favorably and the FEL works fine). I've put about a hundred hours on this backhoe and this is the first time I've had this issue.

Any ideas?

While I'm not super familiar with that particular hoe, if something with clearance of a piece that was otherwise fine at one point then you've got a physical change that alters geometry. This could be anything from excessive pin wear that allows the Piston to settle into the arm to a slight bend in the Piston that causes it to draw that way to a replacement part that isn't exactly to OEM spec that causes this issue. Do you have pictures to illustrate your problem?

 

[TBNDave]

Thanks for the quick response. I replaced the busted fitting and took some pics at the extreme angles that are causing the fitting on the piston to hit the arm.

I have not replaced any parts. Nothing appears to be bent. I like the idea about excessive pin wear; the area on the arm across from the fitting is missing paint, indicating that the fitting may have been rubbing/grinding against this for a while, and finally reached the point where it was so tight that broke the fitting. However, as I look at the hoe, I don't see any pins that, if worn, would lead to this problem. Which pin(s) should I check?

As shown in the last pic, I strapped a 2x4 scrap as a stopgap until I can find a more permanent solution (a stopgap stopgap?).

 

[MtnViewRanch]

I'm not sure if you would consider this a safety hazard or not, but what about turning the cylinder 180* to get the ports pointed away from the stick? :confused3:

 

[Carl_NH]

You can flip the cylinder around so the fittings are pointed up - I can see the top fitting (on the bottom too) then you would not have any clearance issues. The block of wood could put pressure on the center of the cylinder pushing it up..

The only issue having the connections pointing up exposes them a bit more.

Now that I looked at that first picture more closely the dipper stick appears to have about a 1/2" bow in it towards the cylinder, but maybe its just the picture angle?

 

[cglaser104]

You can flip the cylinder around so the fittings are pointed up - I can see the top fitting (on the bottom too) then you would not have any clearance issues. The block of wood could put pressure on the center of the cylinder pushing it up..

The only issue having the connections pointing up exposes them a bit more.

Now that I looked at that first picture more closely the dipper stick appears to have about a 1/2" bow in it towards the cylinder, but maybe its just the picture angle?

I can see a slight arc in the boom on a couple of pictures as well. I'm not sure if that's intentional or not and it would take a helluva lot of force go flex a boom like that. Be that as is may, flipping the cyclindar 180 degrees at the mounting points would resolve the hitting while leaving you a bit more exposed as written above. Just make sure to careful test the hose lengths by gently operating and observing the unit to make sure there aren't other clearance problems or that you are pulling the hoses too tight.

 

[fried1765]

You can flip the cylinder around so the fittings are pointed up - I can see the top fitting (on the bottom too) then you would not have any clearance issues. The block of wood could put pressure on the center of the cylinder pushing it up..

The only issue having the connections pointing up exposes them a bit more.

Now that I looked at that first picture more closely the dipper stick appears to have about a 1/2" bow in it towards the cylinder, but maybe its just the picture angle?

I agree!
The dipper stick appears to have a bow in it that should not be there.

 

[countrybumpkin]

I would at least flip the tube 180. Also here is another thread about a bent dipper stick that may have some helpful info.


https://www.tractorbynet.com/forums/kubota-owning-operating/238666-bh75-dipper-rod-bent.html

 

[Carl_NH]

I would at least flip the tube 180. Also here is another thread about a bent dipper stick that may have some helpful info.QUOTE]

Agree flip the cylinder and go from there - the other thread was a bent cylinder - I looked at the BH77's pics and they all show that fitting being about 1/2" off the dipper frame that's why I took a second look - I cannot imagine what force it would take to bend that dipper stick.

TBNDave, can you put a 5-6' straight edge or even a 4' level on the dipper stick and verify its bent, and have you had this since new or do you have any idea of how this could have happened?

 

[chim]

I agree!
The dipper stick appears to have a bow in it that should not be there.

Could an operator have used the bucket as a "thumb" pressing an object against the dipper stick to bend it?