B8200 HST WILL NOT MOVE FORWARD WITH HOT OIL

[Banjo]

I RECENTLY PURCHASED A B8200 HST WITH LESS THAN 50 ACTUAL HOURS. THE UNIT WAS VERY WEAK IN FORWARD WITH COLD OR HOT OIL. I BROUGHT IT HOME AND THE FIRST THING WAS TO CHANGE ALL THE FLUIDS AND FILTERS, USING ONLY KUBOTA PRODUCTS. I ALSO CLEANED THE MESH SCREEN AND SURPRISINGLY ENOUGH, EVERYTHING WAS VERY CLEAN. I ALSO REMOVED THE HIGH PRESSURE FORWARD AND REVERSE RELIEFS ALONG WITH THE NUETRAL FORWARD AND REVERSE RELIEFTS. THE ENGINE IS STRONG @ 2600 RPM's, THE PTO WORKS FINE AND THE 3 POINT HITCH IS VERY STRONG AND QUICK. REVERSE HAS ALWAYS BEEN STRONG AS WELL. MY PROBLEM NOW IS FORWARD MOTION, AFTER ALL THAT HAS BEEN DONE THE TRACTOR WILL OPERATE NORMALLY PULLING A FINISH MOWER FOR ABOUT AN HOUR. AFTER THAT THE UNIT WILL GET DOWN TO A CRAWL. I MOW IN (M) AND BRING IT BACK TO THE SHOP IN (L). WHILE THE MACHINE SLOWS TO A CRAWL THE PTO AND 3 POINT HITCH WORKS AS IT SHOULD ALONG WITH REVERSE GEAR. I THINK MY PROBLEM LIES EITHER IN THE FORWARD HP RELIEF OR THE FORWARD NUETRAL RELIEF, BOTH OF WHICH ARE CURRENTLY UNAVAILABLE. ANY IDEAS WOULD BE APPRECIATED.
THANKS RANDY.

 

[North Idaho Wolfman]

Sounds like your goin to need to go into the HST and look for something that's not right.
Very odd that it's doing that with only 50 hours on it.
They normally don't fail like that.

 

[ruger1980]

Did you try swapping the forward and reverse relief valves? If not do that and if no change swap the neutral valves

 

[Banjo]

Sounds like your goin to need to go into the HST and look for something that's not right.
Very odd that it's doing that with only 50 hours on it.
They normally don't fail like that.

I AGREE WITH YOU ON THE LOW HOUR FAILURE. I WOULD THINK IF IT IS SOMETHING INTERNAL WITH THE HST IT WOULD DO IT BEFORE 1 HOUR OF RUN TIME AND IT WOULD DO IT IN BOTH FORWARD AND REVERSE. IS THERE A POSSIBILITY THAT ONE OF THE RELIEFS HAS A WEAK PRING ONCE THE SYSTEM GETS HOT? THE OTHER THING THAT IT IS DOING IN FORWARD AFTER IT STARTS TO ONLY CRAWL, I CAN LET OFF OF THE PEDAL AND PUT IT BACK IN FORWARD AND EVERYTHING IS OK FOR A VERY SHORT PERIOD. IT MAKES ME FEEL AS IF I HAVE A VALVE ISSUE THAT IS NOT SEATING OR SEALING PROPERLY. SUGGESTIONS PLEASE.

THANKS RANDY

 

[torch]

My first though was excessive clearances in the pump or motor, but that should affect forward and reverse equally.

Is there a centering mechanism on that pedal linkage? Does the tractor creep in reverse? Does the reverse pedal travel all the way to the stop? Is it possible that something in the linkage (eg: damper rod) is preventing the pedal from moving all the way in the forward direction?

 

[GreensvilleJay]

I'm thinking 'linkage' as opposed to 'HST internals' as reverse works fine, 3PH is fine.
Maybe look at the online parts website to see how stuff 'connects' ? Maybe a free WSM is online ??

 

[johndeerebones]

I'm thinking 'linkage' as opposed to 'HST internals' as reverse works fine, 3PH is fine.
Maybe look at the online parts website to see how stuff 'connects' ? Maybe a free WSM is online ??

Worth a shot. Just so you know though the hydrostat is independent of the hydraulic system. All the hydraulic pump does for the hydro is ensure it gets oil. Not pointing to anything. Low hours on an old machine denotes that a valve stuck somewhere is most likely. Finding it is difficult. I had a working knowledge of the equipment I worked on (mainly JD) and good technical manuals and equipment i didn't have, were on JDs software. Even then it's hard to find them. It is considerably more difficult to find Kubota info like that, even at that some of their manuals are lost in translation, their info leaves some to be desired sometimes. Good luck!

 

[Banjo]

My first though was excessive clearances in the pump or motor, but that should affect forward and reverse equally.

Is there a centering mechanism on that pedal linkage? Does the tractor creep in reverse? Does the reverse pedal travel all the way to the stop? Is it possible that something in the linkage (eg: damper rod) is preventing the pedal from moving all the way in the forward direction?

THANKS FOR THE REPLY. THE HST PEDAL DOES CENTER, NO CREEPING IN REVERSE. BOTH DIRSCTIONS HIT THE STOP AND HAVE BEEN ADJUSTED PER THE OEM MANUAL. ONE OTHER BIT OF INFORMATION, I CAN HAVE THE CRUISE SET WITH THE ENGINE RUNNING 2600 RPM'S AND THE FORWARD PEDAL ALL THE WAY DOWN, AND THE UNIT RUNS FINE FOR ALMOST AN HOUR AND THEN IT WILL START SLOWING DOWN TO A MEAR CRAWL. AGAIN, TO ME THAT ELIMINATES THE HST PUMP AND MOTOR, CLUTCH, HST PEDALS AND LINKAGE. TO ME IT IS ALL POINTING TOWARDS THE HP RELIEFS OR NUETRAL RELIEFS. I AM GOING TO PULL THEM OUT THIS EVENING AND SEE WHAT I FIND. IS THERE POSSIBLY A STRONGER SPRING FOR THE RELIEFS SINCE THERE IS NO REPLACEMENT PARTS? PLEASE REMEMBER, REVERSE, PTO AND 3 POINT HITCH ARE ALWAYS STRONG WHEN THE FORWARD MOTION STALLS.
THANKS RANDY

 

[GreensvilleJay]

whatever parts ,like reliefs, that can be swapped from rev to fwd, would be my choice.
if the problem 'follows' the relief valve, you now KNOW it's the valve.
if fwd is still nogood, 'something' in the 'forward section' is bad.
having proper diagrams will really help.
being 30 years old, 'new' hrs ( +-50, odds are 'something' is 'kinda ' stuck......

 

[torch]

THANKS FOR THE REPLY. THE HST PEDAL DOES CENTER, NO CREEPING IN REVERSE. BOTH DIRSCTIONS HIT THE STOP AND HAVE BEEN ADJUSTED PER THE OEM MANUAL. ONE OTHER BIT OF INFORMATION, I CAN HAVE THE CRUISE SET WITH THE ENGINE RUNNING 2600 RPM'S AND THE FORWARD PEDAL ALL THE WAY DOWN, AND THE UNIT RUNS FINE FOR ALMOST AN HOUR AND THEN IT WILL START SLOWING DOWN TO A MEAR CRAWL. AGAIN, TO ME THAT ELIMINATES THE HST PUMP AND MOTOR, CLUTCH, HST PEDALS AND LINKAGE. TO ME IT IS ALL POINTING TOWARDS THE HP RELIEFS OR NUETRAL RELIEFS. I AM GOING TO PULL THEM OUT THIS EVENING AND SEE WHAT I FIND. IS THERE POSSIBLY A STRONGER SPRING FOR THE RELIEFS SINCE THERE IS NO REPLACEMENT PARTS? PLEASE REMEMBER, REVERSE, PTO AND 3 POINT HITCH ARE ALWAYS STRONG WHEN THE FORWARD MOTION STALLS.
THANKS RANDY

What type of fluid in it? The 3ph is a simple piston and cylinder, so it doesn't care what is in the crankcase. It would probably still work if you filled it with melted butter.

The HST, however, is sensitive to the correct fluid. Can't go wrong with Kubota flavours of UDT, but it does cost more than cheap hydraulic fluid. Perhaps the previous owner was a cheapskate?

Any signs of foaming in the oil once it heats up? Low fluid levels can cause foaming and artificially make the level look higher on the dipstick. Check the fluid level when cold, any difference?

 

[Dieseldonato]

Foaming of the fluid would affect all hydro functions. Forward and reverse. I would hazard the relief valves as well, but fluid is "thicker" when cold. So it won't bypass as easy but will kick a relief easier. Not having one motion (since the hydro pumps fluid bith ways for forward/ revers dependent in swash plate position) typically indicates a relief. This was most noted on older machines that had a manual unloading feature. After the plungers were pushed they sometimes became stuck in the open position resulting in one motion not working. I thin your on the right tract. Take them out and swap them and see what happens.