How to increase HST relief pressure on a CK30

[MotorSeven]

I don't think they are under designed since some of our tractors will spin the tires before going into relief, others here with the exact same model will stall out. I tend to think it is the way they were set or adjusted at the factory. Both my HST's - CK30 and now my Dk40 both spin the tires.

 

[dfkrug]

I don't think they are under designed since some of our tractors will spin the tires before going into relief, others here with the exact same model will stall out. I tend to think it is the way they were set or adjusted at the factory. Both my HST's - CK30 and now my Dk40 both spin the tires.

That is one of the reasons I started this thread. Testing your HST RVs
will tell if your unit is in spec. And if your FWD RV is lower than your
REV RV, then switch them. I think that Tim's method of adding a U-shaped
shim is a good work-around to the welded RV that is installed. How much
increase can you safely allow? No easy answer there, but is does seem that
the gearbox and final drive components may be the same. I have NOT
exhaustively compared part numbers to verify that.

BTW, I have not even tested my own HST pressures; it is certainly
possible that the FWD is low. The failure to spin tires that I have experienced
is in such rare circumstances that I am not seriously inconvenienced.

As for lowering the gear ratios out of the gearbox, that would be hard, and
you would need to do that BEFORE the MFWD shaft driven gear. Changing
all 4 tires to a slightly smaller diameter would help, but with a ground
clearance penalty.

Swapping the whole HST is a possibility, but likely a very costly one.

On the other 2 Kiotis I bought new (CK30 and CK20), I have used them,
but I have not tried the low range/high load/good traction test to determine
if the wheels spin or not.

 

[VictorW]

Tim M and Tinman wondered how much hst RV pressure is to much. If you took it to say 5000#, wouldn't that be like having a gear tractor with no RV. A gear either spins the tires or stalls the engine. I would think that every drive part would handle the torque except for maybe the hst unit. So I think the question is how strong is the hst unit. Mine will spin the not loaded R4 tires in fwd, low range, on pavement and fwd, medium range, on dirt. I have stalled the engine at 2400rpm if the tires bite in and I'm in a higher range than low. I haven't checked the pressures so I can't advise when the RVs open. It would be nice to know how much the hst unit can handle.

 

[Tim M]

That's why I asked if the CK35's (CT235) HST internals were the same as the CK30 (other than the relief valve discussed by SSDoxie above).

If they are then one could infer that it would be fine(or reasonably so) to run the CK30's up to 4300 psi.

MotorSeven,

I agree most people probably are not going to hit the relief before they spin. I have a FEL, backhoe and loaded tires. I hit relief in low gear quite often with no tire spin at 3950 psi (Kioti CK30 RV spec). For what I do I can work around it but it would be nice to get more power to the ground.

Is this a design flaw? Debatable, but I think so.

 

[tinman955]

I did find out that the 40-45-50hp hst bobcat tractors have a 5000 psi which you would assume should plenty enough but I dont know what comparable tractors ie deere, bota ect are running psi wise?

Its a fine balance of power to weight and ofcourse the ability or lack of to transfer the power to the ground in an efficent package, I have no idea how well engineered these Daedong family of tractors are when it comes to being efficent in all ways.

I admit what first attracted me to the daedong family of tractors was price, then I seen one in person and realized what a guy gets for his money, so then I found my local dealer great service carried them and I was sold.

I mean how many individuals have owned more than one compact or utility tractor, or have even ran other brands, to know what is right or wrong?

In my opinion my Bobcat's have been very good equipment, with just a few quirks like some of the topics being discussed. Bobcat is in the infant stage of selling tractors but are no rookie to equipment but i assume as a company the tractor business is separate from their other equipment offerings, they just buy a universal tractor paint it white and they are in the tractor business. Time will tell if they move forward or just let it ride...

 

[IndyIan]

I haven't been able to stall out my HST in low range yet. In mid-range I can use the loader to dig loose materials but not tough stuff.
I don't really understand how the torque output changes with output shaft speed as its possible to really make the engine work hard in high range going fast on the road but at slow speeds the HST goes into relief easily?
I'd like to see all the torque curves for engine rpm and output shaft speed as well as the efficiency curves so I know where to try and run the drivetrain.

 

[BigDogues]

Hi Tim,
I came across you thread on RV mod today. I have had a CK25 since 2006 and have always felt it hit PR far too early. I rarely spin my tires and almost never stall. How has this mod been holding up? Do you think this would work for my CK25? Any input as to what i should see for pressure? I always assumed the CK25 and 30 were exact except for the engine in my model year.
Thanks in advance.

 

[Brozum01]

I have a dk40se hst. The hst has always felt sluggish and goes into relief. Does anyone know where the hst forward and reverse relief valves are located and how to access them?