Kubota RTV 900 help needed

dairybota

New member
Hello Everyone, and thank you in advance for any help or guidance.
I have a 2010 kubota RTV 900 with 2500 hours on it. The problem is that suddenly it would bog down whenever it was in mud, encountered a hill, or basically any time it wasn't going down hill. That being said I am a mechanic at a dairy and this one has me stumped. I did a complete service including the transmission, checked for fuel flow, checked for fuel at the injectors, recently replaced the injectors (after this started actually), jacked the rear end up and did the neutral test (putting it in high gear and pushing the throttle lever to check for wheel movement), checked all the linkages, checked the brakes, checked to ensure all wheels moved freely out of gear. Whenever i drive it, unless I have it at only 1/2 throttle, the engine bogs down terribly and the entire unit slows to a crawl. Any ideas or help would be greatly appreciated! thank you!
 

Doc

Admin
Staff member
Gold Site Supporter
Hi and welcome to our forums. I'm glad you found us.
The one thing you did not mention checking, clogged spark arrestor. That has been a known issue with RTV's and many have removed the arrestor altogether.
 

bczoom

Senior Member
Staff member
Gold Site Supporter
Welcome to the forum!

I'm with Doc on that one. It's a common culprit for power loss.

Thread moved to RTV owners group for greater exposure.
 

bordercollie

Gold Site Supporter
Gold Site Supporter
Hi and welcome !I agree with Doc and Zoom.Check that arrestor for sure. If your muffler has 2 bolts holding on the tail pipe, then it is an internal one that clogs . It has screens and they clog quickly.
The same thing happened to my gas powered blower. - That screen on the muffler was clogged and the power just zapped. bordercollie
 

dairybota

New member
Sorry I forgot to mention that. I had removed the spark arrester quite some time ago so I forgot to mention it. it seems as if the issue is only at higher rpm. this has lead me to believe it may be an internal transmission issue with the primary pump. Am I way off or jumping the gun?
 

bczoom

Senior Member
Staff member
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When was the last time the tranny fluids & filter were changed? What kind of tranny fluid was used? If it wasn't OEM Kubota filters and UDT fluid, that can be the issue.

If fluid is UDT and filters are OEM, then yes, I'd be looking at the primary pump next.
 

dairybota

New member
I service all of my kubotas monthly and due a thorough service (transmission and everything aside from motor oil and air filters which are monthly) every six months. As long as I have done it I have used UDT 2 transmission fluid and kubota filters but I know for sure the person before me did not use kubota filters. I started doing the maintenance on these machine about a year and a half ago. I do have one with a blown motor I have been using for parts, same year and everything. So I could take the pump off of that and put it on this one. What do you guys think? They are heavily used and are often carrying a load greater than what is recommended (they are used to carry milk and water to the calves).
 

ovrszd

Well-known member
So let's "assume" the engine is fine and developing the proper HP/Torque. If the trans pump was bad wouldn't it simply not build speed?? I'm struggling to understand how the pump could cause the engine to bog down??

So let's "assume" the trans pump is fine and properly utilizing whatever rpm speed and torque is applied. If the engine cannot develop full rpms with any load wouldn't that most likely indicate a fuel problem? Maybe starved for fuel? Maybe fuel pump issue not building proper line pressure to the injectors??

Hard for us to diagnose at a distance. Just trying to brain storm with you.
 

ovrszd

Well-known member
So it starts and idles fine?? If so then it's getting solid fuel supplied to the injectors at low rpm. No indication of air in the injector lines.

Are we sure the foot throttle is fully opening the pump rpm lever?? Do you have a hand throttle option?? If so try using it to set the rpms at wide open and then use the foot pedal to engage the tranny.

Actually,,,, a shadetree mechanic test of that issue would be to wire the pump lever to wide open. Crank it up and run the ground speed with the foot pedal and see if you notice any change??
 

ovrszd

Well-known member
Does it act the same in reverse??

Rig up a wire or string to the trans lever where the foot throttle hooks up. Crank it up and pull the tranny lever to full engagement. With the engine at an idle it should stall it. If not that might indicate the tranny isn't building full pressure.

I've not experimented with that and can't right now cause mine is at the farm. But I would assume it would completely stall the engine.

I'm going down there in an hour or so and can try any test you think would help you.
 

aurthuritis

Well-known member
Site Supporter
try running it with the hand throttle all the way open and see if it pulls as it should up to 1/2 foot peddle position. then slowly continue with the foot peddle and see if the tranny is pulling the motor down or the motor is loosing power with increased demand. check your inner air filter as these will look clean and cause this exact problem. make sure you don't have an air intake hose collapsing also. question>>> does the engine smoke black when it pulls down? oh and as a side note>> don't ever consider just because a filter is new that it can't be defective. did this all start just after a major service or has it been creeping up on you?
 
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dairybota

New member
Okay sorry for the delay. I am not on the farm right now but I will be back there tomorrow to do some more testing, I do not have the hand throttle option. It does start and idle just fine. It will also rev up in neutral perfectly fine. No missing or anything. Fuel pressure doesn't seem to be an issue because I pulled the lines from the injectors and turned it over a few times. I do not drive it personally on a daily basis, I only service it. The guys that do drive it regularly aren't very good at communicating the issues when or as they happen. They basically dumped it off and said it wasn't working which doesn't help me either. It will go to full speed when on a flat, dry surface. It does not have the same issue in reverse, only in the forward gears above half throttle. To my knowledge it started about a week ago, which would have been about 3 weeks after a standard service. I believe tomorrow I will wire the throttle full and try to drive it that way. Thanks for all the help so far! I will keep you posted
 

ovrszd

Well-known member
Okay guys, let's brainstorm a bit.

If it's in the hydraulic drive, maybe it's the "forward pressure relief valve"?? Those valves are very basic in design so can't imagine anything breaking. The spring would have to break before it wouldn't try to build pressure?? Maybe something contaminating that valve??

That's the valve that some people tighten a turn or turn and a half to get more torque to the wheels. It's what relieves pressure when in deep mud or trying to climb something and the wheels stop turning. Some have complained theirs won't even spin it's tires in deep mud before that adjustment.

But yet he says it will pull when half throttle or less........ So maybe not???

I still can't see it being the pump. If so it wouldn't be fine in reverse.........

Ideas????
 
Any chance one of your workers has been reading some of our posts on how to adjust these things and tried his own hand at it. Would'nt take much to really screw things up.
 

Kanook

Active member
Idea from way out in left field....seeing as you are not the primary driver.....could this be as simple as the old having to back off on the throttle when pulling uphill that trades ground speed for torque.
 

ovrszd

Well-known member
Idea from way out in left field....seeing as you are not the primary driver.....could this be as simple as the old having to back off on the throttle when pulling uphill that trades ground speed for torque.

He'll figure that out when he wires the throttle wide open as stated in post #13. Thats a very common issue for new drivers. The OP has history with these machines though.
 
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