Kubota L4701 Sometimes Stalls When Moving Forward with HST Pedal

[josiahgarber]

This winter I've been having a problem with the tractor where it starts fine, and then when I press the HST pedal to move forward it stalls. If I leave off the pedal quickly it will not stall and RPMs will come back up. Interestingly, when pressing the pedal for reverse it does not stall.

Is that typical of a seat switch problem? I would have thought that it would prevent me from going forward and reverse not just forward.

 

[jeff9366]

This winter I've been having a problem with the tractor. It starts fine, then when I press the HST pedal to move forward it stalls.

1) In cold temps when you first start the tractor the engine oil is very heavy/thick.

2) When you try to move forward you connect secondary resistance of the cold/heavy/thick hydraulic oil which links the HST pump to the wheels and resistance of cold transmission/wheel bearing oil and grease.



If you increase tractor rpms 10% after the engine has warmed, does the engine still stall? You should not run a L4701 DPF equipped tractor at minimum rpms during cold weather. Increase hand throttle power a tad during cold weather.



Seat switch on all tractors I have operated will kill the tractor engine if not closed. Engine on or off, nothing between.

 

[josiahgarber]

This winter I've been having a problem with the tractor. It starts fine, then when I press the HST pedal to move forward it stalls.

1) In cold temps when you first start the tractor the engine oil is very heavy/thick.

2) When you try to move forward you connect secondary resistance of the cold/heavy/thick hydraulic oil which links the HST pump to the wheels and resistance of cold transmission/wheel bearing oil and grease.



If you increase tractor rpms 10% after the engine has warmed, does the engine still stall? You should not run a L4701 DPF equipped tractor at minimum rpms during cold weather. Increase hand throttle power a tad during cold weather.



Seat switch on all tractors I have operated will kill the tractor engine if not closed. Engine on or off, nothing between.

Thanks. I will check this. What RPMs would be high enough to operate the L4701 in the winter?

 

[Fxfymn413]

It will stumble if the seat switch gets momentarily activated; like hitting a bump for example.

The previous reply is probably correct. I never try to move my L4060 when it is below freezing until it has warmed up for at least 10 minutes at about 1000 rpms. And even then I can tell the hydraulic fluid is more viscous than usual.

 

[jeff9366]

All I can recommend is experiment.

You are in cold winter PA. I am in temperate-winter north Florida. I experience only one or two nights of frost per winter.

 

[Fxfymn413]

What RPMs would be high enough to operate the L4701 in the winter?

My dealer encouraged me to run my 4060 at 2000 rpms or higher to avoid frequent regens.

 

[Fallon]

This winter I've been having a problem with the tractor where it starts fine, and then when I press the HST pedal to move forward it stalls. If I leave off the pedal quickly it will not stall and RPMs will come back up. Interestingly, when pressing the pedal for reverse it does not stall.

Is that typical of a seat switch problem? I would have thought that it would prevent me from going forward and reverse not just forward.

Yes, sounds like typical safety switch issues, but it could be other things. Easy check would be stand up briefly while moving. If it cuts out & back in (if you can sit fast enough) that's a good sign you are on the right track.

Pushing the machine cold isn't great, but shouldn't stall it if it's had a minute or so to warm up. I usually give mine a couple minutes to start to warm up before moving. Oil won't thin out much at that point, but it does get everything lubed up properly. I run them easy for 10 minutes or so before going hard. A working machine generates a LOT more heat than one idling, even at a higher RPM.

 

[nybirdman]

Are you using Kubota branded HST fluids(Super UDt)?

 

[whitetiger]

This winter I've been having a problem with the tractor where it starts fine, and then when I press the HST pedal to move forward it stalls. If I leave off the pedal quickly it will not stall and RPMs will come back up. Interestingly, when pressing the pedal for reverse it does not stall.

Is that typical of a seat switch problem? I would have thought that it would prevent me from going forward and reverse not just forward.

The seat switch appears to be doing its job, but the complaint you have is that the Hydro pedal safety switch is out of adjustment. it is located under the LH running board and just ahead of the LH rear axle housing. You need to unplug the wiring connector from the switch, loosen the jam nut holding the switch, turn the switch in one turn. Tighten the jam nut, plug in the wiring connector and go play.

Edited to correct a typo.

 

[Grandad4]

Very likely it is one of the safety switches or the wiring thereto needing adjustment or something. Probably the one at the foot pedal from your description. Even when cold the engine should have ample power to move forward.