rtv1140 slow up hills, no load on engine

eawood

New member
Hey All, Tons of excellent info here! I've read and read and checked and checked everything I can externally on our RTV and I'm stumped. I'm very familiar with working on hydraulics, mostly dozers and skit steers, but have never worked on a Kubota of an kind.

Its a 2010 1140cpx with 3950 hours
It runs excellent, shifts excellent, neutral is good
Slow speed maneuvering seems reasonable, the pedal is responsive and progressive off idle until about 1/2 throw
On flat ground in any gear from a stop if you mash the pedal to the floor the the engine revs all the way up and it slowly gains speed up to mid 20s. If you have speed and hit a mild 5% grade (on pavement) it struggles to hold 10-12mph with one person in it. Coming up to our house which is a 9-10% grade it slows to 6-8mph. The whole time the engine sounds like its high idling, I have never heard it load up and really start working Never min bog like people describe when promoting the hand throttle In 2wd in low I don't think I could get the tires to spin if I tried, maybe on ice.

What I've done:
new kubota filters and super UDT2
checked forward relief pressure, tough to get an accurate reading but looked to be about 3350psi.
checked the unloading poppet valve (I think this is the one on the right rear of the trans) It seems to be working fine and adjusted fine.
checked the throttle/servo linkage. Looks good, both look to be at max throw at full pedal throw.

any ideas before I tear into the trans?
 

aurthuritis

Site Supporter
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what you need to do is get the transmission up to operating temp and hold it there for a while to get all of the housings real hot before you check the pressures. make sure to check the charge pressure also because a low charge pressure will affect the fill time and volume of the rotating valve assy. then at full rpm adjust the pressure to 3800 psi. if it won't adjust then likely the valve plates are worn. if you get the pressure at HOT oil then you can move on to tweeking the whole system for optimum performance. make sure the engine full throttle rpm is at least 3650 also. another thing is after you get the rpm and pressure up to spec you can adjust the smoke screw just a bit for a tad bit more power.
 

aurthuritis

Site Supporter
Site Supporter
step one-- get the oil hot -- Kubota oil and filters
step two-- check engine full rpm 3650 with peddle against stop and hst speed lever just off of it's full stop.
step three-- with the above checked and corrected if necessary, check hst pressures and adjust as needed
step four-- if performance needs improved adjust the smoke screw and then go through steps 1/2/3 just to confirm.
 

eawood

New member
Not sure on exact temp, it was hot. We drove it around for a good 15-20 minutes first at mostly full throttle.

Rpm is 3590 according to strobe tach, I can bring I up but I can’t believe 60 rpm is causing the issues.

I just pulled apart the forward relief valve and tried to bring pressure up to 3800. Didn’t really budge. It may have brought it up to just over 3400, but a second adjustment did nothing.

I know it’s not the engines lack of power since it never bogs no matter what gear and no matter what you do to the pedal. I’ve messed with a few other 3cyl kubotas and this one isn’t being worked at all.

Sounds like I should check the charge pressure and then on to valve plates?
 

aurthuritis

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Site Supporter
i think you are on the right track. if adjusting the high pressure relief does nothing it is because the internal leakage is probably preventing it from working anyway. remember to readjust it after you install new valve plates. i agree and would hold adjusting the rpm until you get proper pressure as that might change the rpm a little. yes check charge pressure before proceeding. you never get a second chance to record the first information. consider changing the thrust bearings while your in there????
 

eawood

New member
Found my problem. One of the pre charge pump filter hoses collapses when it’s running. Just happened to notice it. I didn’t even bother checking the charge pressure, I’m sure it’s low.

The hose appears to be replaced at some point. It isn’t quite the right length so it has a mild kink when the machine is off and is just standard heater hose. With the machine running the whole hose is flat.

Plan is replace it with hydraulic return hose and I’ll report back. Who knows how many hours the machine has on it with the problem, hopefully it didn’t trash the charge pump.
 
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