Piston assembly 320/09211 JCB Dieselmax SB, standard, genuine (TR)

Genuine JCB piston assembly 320/09211 is used in standard-size bores of the turbocharged SB version of the Dieselmax 444 engine. It is listed with the TR code and kept separate from the IND-coded version of the same number. The photos show the piston with rings fitted; the gudgeon pin and circlips are part of the set.

The piston passes combustion pressure through the connecting rod to the crankshaft. Its rings seal the combustion chamber and control the oil film on the bore. In the turbocharged SB engine the piston crown works at higher pressure and temperature than in the naturally aspirated version, so ring wear shows quickly: blue exhaust smoke, oil consumption, low compression and more blow-by from the crankcase breather. The standard size is for bores that have not been oversized, 103 mm. If a bore is out of the standard tolerance after honing, an oversize piston is needed instead. The gudgeon pin is fully floating and held by two circlips.

Specifications

Compatibility and selection

Suitable for SB-coded Dieselmax engines in JCB 3CX, 4CX and 5CX backhoe loaders; check the code on the engine plate. The same number is also offered as the IND-coded genuine piston and the OEM piston made by Nural. All JCB engine parts are in JCB Dieselmax engine.

Fitting

Pistons are replaced in all four cylinders at once. Before assembly the bores are measured for size and ovality, the ring gaps are staggered and each piston goes in with its mark towards the front of the engine. During the same strip-down the big-end bearings are renewed and the head goes back with the SB top gasket set.