Adjust position control on 3ph

[PaulL]

I have a B2601, about 2 years old. The position control range has never seemed quite right, and perhaps has gotten a little worse (hard to tell).

It is reaching the bottom of the 3ph range at position 4. The mower doesn't really start to lift till about 7. It only goes to 8. It doesn't seem to stop it working - I get full range of motion on the 3ph and on the mower. It just means I guess I get less fine control (and I don't really need fine control).

All of which is a way of saying this doesn't need fixing. But it annoys me.

My WSM has this information, suggesting that I can adjust something by changing the length L of adjusting bolt 3:

Has anyone tried this adjustment, or have any detail to add on how this works? It's night time at the moment, so I may have a play with it tomorrow. It isn't clear what exactly the adjusting bolt adjusts......but seems logical it would be the correlation between the feedback rod and the position control valve.

There's also a complex discussion of how exactly the position control works, and how it has a soft release as it reaches the neutral position. Copied here for entertainment purposes only, I don't understand other than vaguely, and I don't think it's relevant to the adjustment.

 

[TheOldHokie]

I have a B2601, about 2 years old. The position control range has never seemed quite right, and perhaps has gotten a little worse (hard to tell).

It is reaching the bottom of the 3ph range at position 4. The mower doesn't really start to lift till about 7. It only goes to 8. It doesn't seem to stop it working - I get full range of motion on the 3ph and on the mower. It just means I guess I get less fine control (and I don't really need fine control).

All of which is a way of saying this doesn't need fixing. But it annoys me.

My WSM has this information, suggesting that I can adjust something by changing the length L of adjusting bolt 3:
View attachment 93852

View attachment 93851

Has anyone tried this adjustment, or have any detail to add on how this works? It's night time at the moment, so I may have a play with it tomorrow. It isn't clear what exactly the adjusting bolt adjusts......but seems logical it would be the correlation between the feedback rod and the position control valve.

View attachment 93853
View attachment 93854 There's also a complex discussion of how exactly the position control works, and how it has a soft release as it reaches the neutral position. Copied here for entertainment purposes only, I don't understand other than vaguely, and I don't think it's relevant to the adjustment.

View attachment 93855
View attachment 93856

The adjustment you are looking at sets the STOP limit for the TOP position of the lift. You are contemplating adjusting the operation of something you dont understand. If it aint broke dont fix it until it is.

With nothing on the lift fully lower the 3pt. The ends of the lift arms should be very nearly touching the ground. Now slowly start to move the lever upwards and note the position where the arms begin to lift. That will tell you where the bottom of the position control range is. It probably wont be position 1 on the guide plate but I will bet that it is lower than 7.

Bring the lever to the top. If the lift arms come to the full up position and then stop without tripping the pressure relief valve the feedback rod is adjusted correctly. If the arms stop before they are in the full up position or they dont stop and the hydraulic relief valve opens the linkage needs to be adjusted.

Dan

 

[PaulL]

The adjustment you are looking at sets the STOP limit for the TOP position of the lift. You are contemplating adjusting the operation of something you dont understand. If it aint broke dont fix it until it is.

Aha. Exactly the information I needed. The manual said it was an adjust, it didn't say what it adjusted. You are correct, I don't have a problem with the top, so that doesn't need adjusting.

With nothing on the lift
fully lower the 3pt. The ends of the lift arms should be very nearly touching the ground. Now slowly start to move the lever upwards and note the position where the arms begin to lift. That will tell you where the bottom of the position control range is. It probably wont be position 1 on the guide plate but I will bet that it is lower than 7.

The mower moves at around 7. I expect that's deliberate - there's movement in the 3ph before the mower linkage engages, meaning the 3ph doesn't have to be all the way down when the mower's all the way down.

The 3ph itself is all the way down at around 4. As I noted, it works fine, it just seems that 1-3 have no purpose if they're not resulting in any movement of the 3ph.

Bring the lever to the top. If the lift arms come to the full up position and then stop without tripping the pressure relief valve the feedback rod is adjusted correctly. If the arms stop before they are in the full up position or they dont stop and the hydraulic relief valve opens the linkage needs to be adjusted.

I'll check more thoroughly tomorrow, but in general it seems to me that the hitch goes all the way up - I'm not lacking travel at the top.

 

[TheOldHokie]

Aha. Exactly the information I needed. The manual said it was an adjust, it didn't say what it adjusted. You are correct, I don't have a problem with the top, so that doesn't need adjusting.



The mower moves at around 7. I expect that's deliberate - there's movement in the 3ph before the mower linkage engages, meaning the 3ph doesn't have to be all the way down when the mower's all the way down.

The 3ph itself is all the way down at around 4. As I noted, it works fine, it just seems that 1-3 have no purpose if they're not resulting in any movement of the 3ph.



I'll check more thoroughly tomorrow, but in general it seems to me that the hitch goes all the way up - I'm not lacking travel at the top.

Crucial to understanding the 3pt - the lift arms are not a fixed connection to the cylinder. Raising them by hand will not extend the cylinder

The attachment point of your mower is in the middle of the lift arm range and when you manually lift the arms to hook them to the mower the cylinder does not extend. That is why it does not lift until the cylinder extends far enough to contact the lift arms. If you had an attachment that hooked up lower in the lift arm range it would start to raise at a lower lever position.

As long as the lift comes to the top and shuts off the feedback is adjusted properly.

Dan

 

[mikester]

 

[PaulL]

Crucial to understanding the 3pt - the lift arms are not a fixed connection to the cylinder. Raising them by hand will not extend the cylinder

The attachment point of your mower is in the middle of the lift arm range and when you manually lift the arms to hook them to the mower the cylinder does not extend. That is why it does not lift until the cylinder extends far enough to contact the lift arms. If you had an attachment that hooked up lower in the lift arm range it would start to raise at a lower lever position.

As long as the lift comes to the top and shuts off the feedback is adjusted properly.

Dan

Aha. So if I take the mower off entirely, then I'd expect the arms to drop lower, and therefore to use more of the position control range?

 

[TheOldHokie]

Aha. So if I take the mower off entirely, then I'd expect the arms to drop lower, and therefore to use more of the position control range?

I have never actually tested it but I expect so - try it and see.

Dan

 

[PaulL]

I have never actually tested it but I expect so - try it and see.

Dan

Tested today. No, the mower and the 3pt arms aren't solidly attached. The 3pt continues to drop after the mower reaches it's stop. There's a slide on the relevant lifting arm.

Independent of the mower, the 3pt arms (and the associated lift arms) don't move until about 4-5 on the position control. It seems very un-Japanese to build a position control lever that has twice as much range of motion as it needs. So I suspect there's a way to adjust it. I will continue to investigate.

 

[North Idaho Wolfman]

Paul it's just the way it is with that model, it's not a proportioning valve it's a simple on / off valve there really is not much reason for there to really even be any numbers on the three point lever.

 

[PaulL]

Hmm. Depends what you mean by proportioning valve. It is definitely not quarter inching like a BX, it is a proper position control. The excerpts from the workshop manual I pasted above even explains how the feedback loop works with the feedback linkage.

It seems unusual that you would make a position control lever that only operates over about half of it's range. As I noted above, that's a very un-Japanese thing to do - they would normally make the range appropriate to the thing it's controlling. It seems to me to be reasonably trivial to move the linkage under the position control lever a little closer to the pivot, causing you to need to move the lever further to get the same effect. I could understand if it was a little bit off - tractors get used hard and things go out of adjustment. But using only 50% of the range seems unusual. Moving the lever connection closer to the pivot point would also increase the leverage, making the lever easier to move, which would seem sensible on a lever that will likely get sticky over time.

Anyway, as noted it doesn't affect any actual functioning of the tractor, it's just something that seems wrong somehow.

 

[TheOldHokie]

Hmm. Depends what you mean by proportioning valve. It is definitely not quarter inching like a BX, it is a proper position control. The excerpts from the workshop manual I pasted above even explains how the feedback loop works with the feedback linkage.

It seems unusual that you would make a position control lever that only operates over about half of it's range. As I noted above, that's a very un-Japanese thing to do - they would normally make the range appropriate to the thing it's controlling. It seems to me to be reasonably trivial to move the linkage under the position control lever a little closer to the pivot, causing you to need to move the lever further to get the same effect. I could understand if it was a little bit off - tractors get used hard and things go out of adjustment. But using only 50% of the range seems unusual. Moving the lever connection closer to the pivot point would also increase the leverage, making the lever easier to move, which would seem sensible on a lever that will likely get sticky over time.

Anyway, as noted it doesn't affect any actual functioning of the tractor, it's just something that seems wrong somehow.

If they made the slot in the guide plate 2" shorter at the bottom and things moved immediatly would it be "fixed"?

If they made the slot 2" longer and you had more free travel would it be "more broken"?

I think you are making more of this than it merits. As is you currently have "infinite" control of lift height from full down to full up. If the extra travel is too annoying to ignore buy another stop and put it on the slot to limit the "excessive" down travel and call it "fixed".

Dan

 

[nbryan]

My B2650's position control has no effect lifting the arms (with nothing attached to them) until the lever is brought to about position #4. I also asked here about this and it seems all that Kubota CUTS that sport position control 3-point are about the same, no lift until around position 4.
The why of that is for a Kobota engineer to answer.
I'm quite used to this, my hand reaches and pulls the lever to the #4 start point without thinking anymore.