1/4" Valve Problem on B7800?

[N1ST]

On my tractor, the Full up and Full down work, but when using the full up, the engine strains a bit (with no implement) - is this normal?
Than manual pg 39 says if noises are heard when implement is lifting after control lever has been activated, it's not adjusted properly. I see the double nuts at the end of the control rod (yellow metal part) and what appears to be a stop accross from it on the gray painted part, but that's all I see to adjust.

The 1/4" positions do not appear to work. When I move the lever to the down 1/4" position, nothing happens. When I move the lever to the up 1/4" position, the engine strains, but the arms do not move. Is there a simple adjustment for this?

 

[N1ST]

...crickets chirping...

Ok, this is obviously a problem only experienced by the truly tractor-unlucky. I'll pose this question then to any mechanic familiar with the innerds of kubota transmissions that use 1/4" inching valves. What could possibly cause this problem??

 

[Bob_Young]

N1, the Quarter Inching stops on the 3PH control quadrant are adjustable. If nothing happens at the QI position, the stop must be loosened (there should be a small bolt nearby) and moved slightly in the direction of the full travel stop. You should set it at a spot where you get a slow and easily controllable movement of the hitch when the control is held against the QI stop.

To get some idea of where this might be, carefully move your control beyond the current QI stop position toward full up (or down). Once you get the hitch moving slowly but continuously, you're in the balllpark. Make sure you've got the underseat valve opened at least a full turn when you set the Down QI stop...otherwise the slow movement might be due to restriction through the valve rather than 3PH control position.

Once you see what this gives you, you'll realize that "Quarter Inching" is really a misnomer. I had the same problem with the B7610 on delivery.

The engine will strain a bit when the control is held in the Full Up position. While held in that position, you might also notice that you can no longer lift the FEL (if you have one). Apparently the 3PH hydraulic circuit gets flow priority. Something to remember if one day your FEL stops working.
Bob

 

[N1ST]

Thanks for the reply. A few questions...

I did try moving the QI stop and did notice a point where the arms moved (up) slowly. But I did not find a spot that when the lever was moved to, the arrns would move up a little then stop.

So are you saying that once I find the slow movement spot, I should continue moving the stop slightly until I find a spot where when I move the lever to it (quickly), the arms will move somewhat then stop moving, or will the arems continue to move slowy as long as the lever is held to the stop? I'm still confused as to whether this is a "slow continuous movement feature" or a "move then stop feature".

Regarding the engine straining. It does not strain at all if I move the lever to full up. It does strain if I move the lever to the "slow up" spot. ...especially at idle. At higer revs, the strain is less noticable. Does this sound normal? I don't want to be using it in such a way that's bad for the pump or engine.

Thanks

 

[Dr. Bob]

N1
I have a B7800 (03) and it behaves as yours does. I have never had any problems with it and have just learned to work with it as it currently performs.

Are you assuming the "quarter inching" means that if you move the controller to that position that it will move 1/4" and then stop? If so, I have never assumed this or seen it work this way on my machine. The "quarter inching" is just a term for the very slow movement of the 3-point.

 

[herringchoker]

My B7800 also behaves as yours does. As Dr. Bob says, "quarter inching" is just a term for the very slow movement of the 3-point. It is not a "move then stop feature" as you describe it. It takes a bit of getting used to, but I find it works great for me.

 

[N1ST]

Ok thanks guys, I'm starting to feel better about this.

herringchoker - Does your engine bog down a bit at idle when using the QI? Mine does, but it doesn't bog down while idling when moving arms at full speed (going up). I wonder, does this mean it's best to use the QI position at high rpms to go easy on the engine.

 

[herringchoker]

No, I haven't noticed it straining, but then I seldom use it at idle. Now you've got me thinking and I will have to try it. Trouble is, the tractor is 50 miles away and I won't see it until the weekend, weather permitting. I will try it and post back.

 

[herringchoker]

Well, I tried it today at idle (but with a 60" bushcutter attached). With the engine at idle and the TPH lever in the 1/4 inching "up" position, the TPH lifted very slowly and steadily until it was fully raised. The engine did not bog, but I noticed a slight change in sound (perhaps in the hydraulics??).

 

[N1ST]

Well, I tried it today at idle (but with a 60" bushcutter attached). With the engine at idle and the TPH lever in the 1/4 inching "up" position, the TPH lifted very slowly and steadily until it was fully raised. The engine did not bog, but I noticed a slight change in sound (perhaps in the hydraulics??).

Yes, that's probably what I'm hearing also. It's tough for me to tell if it's just the hydraulics or both. If I rev to 1500+, I hear nearly no change in sound. Thanks for checking.

Now that I understand that the feature doesn't move 1/4" or whatever small amount then stop - it continues to move, I'm fine with this. Becuase I can set it for any rate of up by adjusting the tab stops and any rate of drop by adjusting the black "close" knob, I see no real advantage of position control (which I've used) over this.