Kubota GL21 hydraulics, PTO & implements: what can you do with 21 hp?
Suitable for the entire Kubota GL series (Grandel): GL19, GL21, GL23, GL25, GL25K, GL26, GL27, GL29, GL32 and GL33 (also GL23DJ and GL27DJ, and the Hinomoto NX series).
The hydraulics and PTO of the Kubota GL21 make this compact tractor a real workhorse. In this blog you'll read how the lift linkage and Monroematic depth control system work, which PTO speeds are available and – very practically – which implements you can realistically hang on a tractor of this class.
Kubota GL21 three-point hitch and position control
The GL series has a category 1 (JIS) three-point hitch with position control: the position of the lift lever determines the height of the lift arms, and the hitch holds that position. Pushing forward lowers, pulling back lifts. On the M and MA versions there is also Monroematic: an automatic depth control system that uses the dial on the control panel to keep the working depth of, for example, a rotary tiller constant, with a sensitivity switch (off / standard / sensitive). The manual gives a recommended setting for each job: shallow working (5–8 cm) with the dial towards "shallow", normal tilling at 8–15 cm around the middle, and deep ploughing (15 cm and more) towards "deep" with the position lever in the lowest setting.
How strong are the hydraulics?
The official Japanese type approval report of the GL25 (same hydraulic system as the GL21) gives these values, as an indication for the whole series: lift force of approximately 1,135 kgf at the ball ends and 935 kgf further behind the lift frame, a pump output of 21.1 l/min and a system pressure of 14.6 MPa (149 kgf/cm²). More than enough for a rotary tiller, plough, tipping trailer or pallet fork in this class. The maximum drawbar pull during that type approval was approximately 800 kgf on concrete.
Kubota GL21 PTO
| Component | Specification |
|---|---|
| Shaft type | JIS 35 mm, 6 splines |
| GL21 speeds | 568 / 803 / 985 / 1,304 rpm at 2,600 engine rpm |
| Reversible PTO (X version) | 803 rpm, counterclockwise |
| Operation | separate PTO lever, engaged with the clutch depressed |
Please note: this is a Japanese domestic machine. In practice, the second setting (around 800 rpm) is used for many European 540-rpm implements by slightly reducing the engine speed – calculate this per implement, especially for flail mowers and rotary tiller units. Always fit the PTO protective cap after use.
What can you realistically do with 19 to 33 hp?
Important to know: of the 21 hp at the engine, the GL21 retains around 16 to 17 hp at the PTO (in the GL25 type approval: 17.2 kW PTO power from 25 engine hp). For PTO implements that figure matters, while for pulling work the weight (over 1,000 kg) and 4WD are what count most. Practical guidelines for the GL21: a rotary tiller of 1.10 to 1.40 m, a flail or cyclo mower up to approximately 1.50 m, a single-furrow reversible plough, a tipping trailer of 1.5 to 2 tonnes, a wood chipper for branches up to ~8 cm or a snow blade of 1.50 m. The GL29–GL33 pull one size up: tillers up to 1.60 m and two-furrow ploughs. Anything heavier can overload the clutch and hydraulics – it's better to choose one size smaller and work a notch deeper.
Working on slopes and with heavy implements
With a heavy implement on the lift, the front becomes light: use front weights and keep an eye on the tipping limit on slopes (the type approval records a static tipping angle of 37 degrees). Always lower an implement when parking and lock the position lever.
