RTV500 HST Shifting

[westbrooklawn]

TWO GUNS - check your pm

 

[MessickFarmEqu]

RTV owners...Stonehaller and I have had some discussions about this, and his help has been outstanding.

My question is this: When you are going uphill with the gas pedal mashed, does your RTV downshift (like a regular auto tranny), or do you have to let up on the gas to cause the downshift? In my case I have to let up on the gas, in Stonehallers case he doesn't.

You do need to leave off the pedal.

 

[Stonehaller]

You do need to leave off the pedal.

I was hoping a Kubota dealer would join this discussion. I ask you to take a look at the functional hydraulic diagrams in the shop manual and explain the function of the variable motor.

Here is my interpretation. The peddle changes the swash plate angle of the pump which, of course, changes the ratio of the transmission. The pump drives two motors. One motor has a fixed angle swash plate and the other motor has a variable angle swash plate. The variable angle swash plate motor will also change the ratio of the transmission. The variable motor is not controlled by the peddle, but rather by the hydraulic pressure in the transmission. As the hydraulic pressure in the transmission goes up, due to increased load on the transmission from acceleration or a hill, then the higher pressure will increase the swash plate angle of the variable motor changing the ratio of the transmission to a 'lower gear'.

 

[bigdeer2000]

I would check the spark arrestor to see if it is clogging up. mine was at less than 50 hrs. sure robs your power when clogged.

 

[mstordahl]

You DO NOT have to lift up on the pedal if the HST is set up correctly from pdi. On the Kubota hst your foot is not directly connected to the swashplate in the trans, it goes through a reaction valve first which senses hst pressure to tell the pump when to de stroke. Under full load, the engine should pull down a little, but not bog, and you definately do not have to back out of the throttle. The system was designed to take care of these types of issues, but it only will work as designed if set up right. It is an easy adjustment to make too.

 

[mstordahl]

stonehaller, your interpretation is correct. That is how this HST works on the 500, 900, 1100 and 1140.

 

[timswi]

You DO NOT have to lift up on the pedal if the HST is set up correctly from pdi. On the Kubota hst your foot is not directly connected to the swashplate in the trans, it goes through a reaction valve first which senses hst pressure to tell the pump when to de stroke. Under full load, the engine should pull down a little, but not bog, and you definately do not have to back out of the throttle. The system was designed to take care of these types of issues, but it only will work as designed if set up right. It is an easy adjustment to make too.

This is getting confusing. Dealers and some other owners say that letting up is necessary, others say no. What adjustment would you do? I would prefer full throttle downshifts as letting off the throttle also lowers the RPMS which causes lower power...VERY annoying.

Need Kubota engineering to weigh in here.

 

[737pilot]

Timswi I quit trying to make the machine perform outside of the design characteristics. Its a underpowered golfcart and its not a tractor or a honda big red, polaris ranger, actic cat or Rhino. Its a utility vehicle that runs like its powered at times with a rubber band or Radio Controlled airplane gas engine. With all that said I love the darn thing and it does what it does best. Gets me around the hutin camp and also hold alot of ice cold beer in the back. Your machine is operatiing exactly like the machine was designed to operate. There isn't anything wrong with it. I myself would like to feel some more power so eventually im probably going to switch brands. Just ride it and use the heck out of it. It is a tough machine and you can't break it. I run my hard as I can with no complaints.....like i said before it is what it is and if you think about it its not all bad. I actually love mine. Yes we all know it's underpowered.

 

[timswi]

Timswi I quit trying to make the machine perform outside of the design characteristics.

737, I don't expect too much, just trying to get some straight answers...This whole idea of letting up on the gas just makes no sense. Was going up a hill in the woods the other night and ran out of RPMS due to letting up for downshifts. That part of the machine is really stupid...I'm with you in that I really love everything else about this little machine. Just this part makes no sense at all and there seems to be a wide disparity of opinions on proper performace.

 

[737pilot]

Timswi you say you run out of rpms going up a hill. I run out just going up the ramp on my 5x10 trailer. It won't make it uop the ramp in high gear unless you get a running start. It's lacking alot of tourqe in high gear. I think the HST is good in theory but is very inefficient in power transfer. This engine is a 450cc motor ok. I have a 250cc Yamaha timberwolf thats basically half the motor and it will kick the RTV 500's behind. Anyhow as far as the peddle thing I let off soemtimes to see if it helps on a hill and i can hear it pick up RPM's but its really not noticble on the speedo so I just keep it floored everywhere I go. I get great gas milage and my rattle sound is still there if you teally listen for it but like i said earlier much better with the new alternator. I know your frustrations brother. You just want the thing to act like a teenager not a 100 year old man. Take care and run the heck out of it...You won't hurt it.