Yes pedal all the way down travling / just abit pushing against the tree / when travling if i let up on the peddle just a bit RPM cum pack up / filters oil less then 20 hr old / there are apparently high psi relifes valves inside ?????? maybe
Ok, forget what I said about filter or kinked lines. That wouldn't bog down the engine.
Back to the pedal position: As I said earlier, pushing the pedal slightly is like putting a gear transmission in 1st gear. Pushing the pedal all the way is like putting the tranny in high gear.
To review:
in "1st gear", the tires will spin when pushing against a tree. In top gear, the motor will bog down going up the slightest hill
but recover if you "downshift" (ease up on the pedal a bit).
Engine itself seems to have normal power, in that it will run a heavy PTO load alone without bogging down. But we don't know for certain exactly how much HP that load is actually applying.
Problem is slightly less apparent once the engine and fluids are warmed up.
Fluid and filter was changed without apparent effect.
Tractor rolls easily in neutral.
I am not an expert, but wondering out loud in reverse order:
While the tractor rolls when no torque is applied, jacking the tractor off the ground might reveal an issue that only occurs under torque on the driveline. EG: worn bearing.
By "fluid" I assume you mean the transmission fluid. What brand/weight of fluid? The improvement when warm may indicate that the problem is reduced as the fluid thins a bit as it warms up. Discount fluid may not be right for the HST.
Any chance a local farm supply/tractor repair shop would have a PTO dyno available to confirm available engine power? Perhaps the bat-wing just doesn't apply as much load on the engine as you think it does. Bear in mind that an HST is less efficient at transmitting power to the ground than a gear drive. The fluid heats up because some of the engine power is being converted to heat pushing the fluid around instead of usable power to the ground.
Alternatively, while you changed the injectors, etc., have you done any investigation of the engine mechanical health, such as a compression test? Checked the air filter/intake for blockages?
I don't know if it's even possible to move the HST swash plate too far, but could this be a pedal adjustment issue? (Maybe one of the Kubota mechanic can weigh in on this here). I assume the tire sizes are stock? (Larger tires would require more torque to turn). Can you verify that the transmission range is actually shifting when you move the lever? (eg: mark tires and measure rpm of tire in each range with tractor jacked off the ground at idle).
