Kubota RTV900 lack of power

[murphyzoo]

I'm having trouble with a new-to-me 2005 Kubota RTV 900. It seems quite under-powered. I'm well aware that this diesel RTV is meant as a work-horse and not a speed demon. Our main goal with this is to be able to drag our horse arena with the ABI Arena Rascal Pro. The drag is built so that a 750cc ATV should be able to tow it. The ABI company said that a RTV900 should be more than sufficient.

The engine appears to run ok - it revs up and sounds smooth, but just feels underpowered. We have a slight hill on our property and the RTV has a hard time going up it in M and sometimes in L. If we stop on the hill, it's near impossible to get going again. Under load (towing the arena drag), it is very apparent the RTV doesn't have the power it should - we know it isn't a tractor and aren't trying to do something an ATV couldn't do. We also seem to notice that it loses even more power when it fully warms up. I'll drive it down our street in H gear and use a GPS to measure the speed. Once warm, the speed will be 3-4mph slower (this seems odd to me).

We picked it up with about 2400 hours on it. I did a full fluid change using Kubota SuperUDT2 and Kubota brand filters. I added a high-rise air intake and have checked the exhaust spark arrestor. I also added the hand-throttle option based on my local dealer's recommendation so that I can rev up the engine separate from driving the transmission. I've read several of the articles on RTV's with low power, so I know not to just mash the throttle to the floor. With the break off and the RTV in neutral, it rolls smoothly, so I don't think the brakes are an issue.

What else should I check on this RTV? Would you guess this to be an engine power issue or a transmission problem getting the power to the wheels? What's the best way to find out where the issues are?

Thanks

 

[texasjohn]

:welcome:
Well worded and complete first post.
I assume you are in 4 wheel drive when dragging the arena.
When in low range, in the arena where I assume there is sand, do you maintain traction or do your wheels spin?
Does the engine bog down (quit/slow down) or keep running fine when it "feels underpowered?" Exactly what are you doing when this happens.

You have done all the maintenance things, including hand throttle, that I can think of.

just FYI, my RTV will not spin tires like a drag racer from a standing start. It will start off slow and somewhat slowly pick up speed depending on loading and/or land incline. If load is too great/incline too steep/gear selected too high, then it just sits there and engine bogs down. Shifting to a lower gear very often results in the vehicle moving right off without issue. I have never found an incline where it would not move off in 4wd low range and starting off slow on the pedal. Your measured slower top speed when hot does concern me, but haven't measured my speed same way, thus don't know what it does.

 

[murphyzoo]

The arena is mostly dirt with some sand. We drag the field in 4wd and Low gear. The RTV maintains traction - the wheels don't spin. It just can't seem to pull the drag through the dirt (it isn't hard packed). I have a skid steer that I use when the ground is hard packed - I'm trying not to ask too much of the RTV. The engine will be revved up and you can feel the RTV wanting to move forward, but it just doesn't have the power to overcome the drag force. While I can feel it trying to move, it doesn't.

I'll have to get out there and pay more attention to how "bogged down" the engine gets. I don't remember the engine rpm / sound really sounding like a bogged down engine (like my lawn mower trying to mow grass that is too tall/wet).

The slower top speed when it is warm is definitely a weird symptom. Hopefully, it is not a red herring. I've duplicated the experiment in H and in M a couple of times and have verified the speed drop after it fully warms up.

 

[texasjohn]

Well, I admit confusion...seems you are doing all the right things to me. Only thing I can think of is to see if you can find someone in your area who has a RTV900 and see if theirs exhibits the same behaviour or if it can pull the drag. While I have pulled a 1000 gallon metal tank trailer full of water over my property and up a reasonably steep hill (never figured out total rolling weight), I have never tried to pull a drag with it. My RTV has pulled everything I've hooked it to.

Let us know what you finally figure out.

 

[murphyzoo]

I've got a friend that has a compression tester that he used on his Kubota tractor. We'll check the compression and see if the motor appears ok.
I don't have the pressure gauges to test the transmission pressure. Not sure if it is worth buying the gauges / hoses and figuring that out or taking the RTV to the dealer. For those of you that bought the pressure gauges, was it worth it?

Are there other things I can check? I'm wondering if there is a easy way to check the linkages - everything looks fine there though (I haven't measured, but visually inspected).

 

[candoarms]

You've probably already checked this, but your fuel filter is where I'd start with this issue. Your problem is very common with smaller diesels....not just Kubota.

It sounds to me as though you're getting enough fuel to keep your engine running, but maybe not enough to generate any power. Remove the fuel filter and replace it. This is usually the culprit.

Joel

 

[murphyzoo]

Thanks. I had read the fuel filter was one of the possible items. It was replaced when I did the other filters/fluid changes. I saw no change from the old to the new filter.
With 2400+ hours on the RTV, I'm worried something more expensive (engine rebuild or transmission overhaul) is needed. I'd hate to spend the time on rebuilding the engine to find out it wasn't needed. I have someone that can help me rebuild it (he rebuilt his Kubota tractor engine - very close to the same one), but neither of us know much about the hydrostatic transmissions and diagnosing problems there.

 

[texasjohn]

I just remembered this thread....

http://www.tractorbynet.com/forums/atvs-utility-vehicles/329697-kubota-rtv-900-1100-owners.html?highlight=rtv%20rear%20nut#post4028735

It says, in part....

This is a quote from orange tractor talks website.(For those running RTV,s there has been a increase in the torque specs for the nut on the rear axle.We have had some spline failures here so this is likely important !Remove the plastic hub cover in the center of the rear wheels,remove the cotter pin and torque the nut 140 lbs(both sides)kubota also has a new drive shaft available for the front drive (transfer case to front diff)It is reasonably priced and a vast improvement over the original)End quote.This happened to my 2006 Kubota RTV 900 this past week with 610 hours on the clock.It is in the shop as we speak.The repair bill set me back $932.Just a heads up you might want to retorque your rear axle nuts to 140lbs per side as stated.Hopefully doing this will save you a few $$ in a repair bill such as mine.

Something to look into...

 

[PapaPerk]

Something is wrong with it. They have plenty of pulling power for a drag. Maybe trans issue. I doubt it's an engine issue. Best bet to fix fast is a trip to the dealer. Good luck!

 

[murphyzoo]

Thanks for this information. I'll definitely work on torquing the nut to 140 ft/lbs for the axles.

As far as the new drive shaft for the front (front propeller shaft), I ended up having to add one of these to the RTV. Somehow, I completely missed this during my inspection before buying the RTV (I guess I missed a lot of things). The RTV I bought didn't have a front drive shaft. :-(
When I test drove it, I put it in 4WD and everything worked (no noises), but I didn't do anything to specifically verify the 4WD put power to the front wheels. Anyway, that's one of the other things I've done.

Overall, I think I'll be really happy with this RTV as soon as I get the power issue resolved. I don't have the power-dump bed in the back, but that's ok with me.