Overhauling the Kubota 05 Series: Cylinder Head and Engine Block

Want to overhaul your Kubota 05 series engine instead of replacing it? That's often the smartest choice: as long as the block and crankshaft are in good condition, an overhaul kit and a good cylinder head will bring the engine back to top condition for a fraction of the price of a new engine. In this guide you'll learn when an overhaul pays off, how to correctly remove and install the cylinder head, and which adjustment values to use.

Suitable for the entire series: D905, D1005, D1105, D1305, V1205, V1305 and V1505 (incl. turbo -T/-TE and versions -E/-E2B/-E3B/-E4B).

Overhaul or replace the Kubota 05 series engine?

The choice depends on where the problem lies. First perform a compression test and a coolant pressure test to confirm the diagnosis.

• Problem at the top (white smoke, coolant loss, warped or cracked head after overheating) while compression is even: this can often be resolved with a complete cylinder head, without opening the block.
• Blue smoke and oil consumption, uneven compression: then the wear is in the piston rings, pistons, or valve guides. This calls for a complete overhaul.
• Low oil pressure, bearing noise, metal particles in the oil: then the block needs to be opened for the bearings and possibly the crankshaft.

If the block and crankshaft are still within tolerances, an overhaul is almost always more cost-effective than a complete (exchange) engine.

Removing and installing the Kubota 05 series cylinder head

Removing the cylinder head and reinstalling it correctly is the core of most overhauls. The key rules:

• Always use a new head gasket. Never reuse the old one.
• Do not install the pin-pipe upside down and do not fit an O-ring on the pin-pipe.
• Apply engine oil to the thread of the head bolts.
• Tighten the bolts in multiple steps, from the center outward in a crisscross pattern, following the prescribed sequence (3-cylinder 14 bolts, 4-cylinder 18 bolts).
• Final torque: 64–68 N·m (6.5–7.0 kgf·m).

Tightening sequence of the cylinder head bolts: from the center outward in a crisscross pattern, in multiple steps up to 64–68 N·m.

Good to know: after installation and warming up, the head bolts do not need to be retightened, and the valve clearance does not need to be readjusted.

Kubota 05 series adjustment values: valve clearance and top clearance

Two values are crucial when installing the head and pistons:

Top clearance is the distance between the piston crown and the head surface at top dead center. If this is incorrect, it indicates the wrong head gasket thickness or non-standard pistons; always check this during an overhaul.

Kubota 05 series overhaul kit: what's included?

A complete overhaul kit generally includes the wear parts you replace during a major service: pistons and piston rings, bearings, and a complete gasket set. If you want to keep costs down and the top end is still in good condition, there's also the in-frame overhaul kit, which lets you replace the pistons and rings without removing the entire block from the machine. Individual parts are also available separately: pistons, connecting rod bearings, and the bearing/piston pin bushing.

Kubota 05 series: parts are not interchangeable between models

This is the most important pitfall when overhauling. Because the bore differs per model, head gaskets and pistons are not interchangeable between models. A 72 mm piston from a D905/V1205 does not fit in a 78 mm block from a D1105/V1505, and the head gasket from a D905 does not seal properly on a D1105. Always order parts based on the exact engine type and serial number. Also note: the 05 series has dry liners, so coolant in the oil comes from the head or gasket, not from a "cracked liner".