Kubota B3150 4in1 Bucket wont lift under certain conditions

[Scrumpy]

Hi, B3150 with genuine 4in1 bucket, low hours on unit. Was working fine but bucket wouldnt lift more than partway occasionally. not very often . BUT lately, bucket stops lifting fully after 6 or 7 lifts from cold, and wierdly, will only lift fully if I throttle back to idle, drop the bucket with the release hydraulics function (push control lever fully forward to let bucket drop by gravity), then I can lift bucket OK...until I increase revs then bucket will stop a bit under halfway up. straining noise as if hydraulics working but something holds it back. All other hydraulic functions are fine, recently serviced, drained hydraulic fluid and refilled with Genuine Kubota fluid, level is at top notch on the dipstick on transmission case at rear of tractor. Really strange - has anyone got any ideas please? Only way to reactivate lift function properly is as above, throttle back to idle, release bucket by gravity, then it works a treat. Hydraulic lines are Ok and have not been removed at all. And position of TPL control doesnt affect this problem.

 

[mikester]

Loose linkages on your joystick?

 

[GreensvilleJay]

Maybe 'junk' in the pressure release of the 'up-down' spool valve ?
Maybe the spring is broken ?
For sure remove whatever covers are there and SEE that proper range of joystick IS happening.

 

[North Idaho Wolfman]

Disconnect and reconnect all of the quick disconnects on the hydraulics, Including one behind the seat if equipped with a BH loop.