Piston assembly 320/09249 standard, aftermarket, option 2

For the JCB Dieselmax 444 (SD) engine: piston assembly 320/09249, standard, an aftermarket part. The photo shows the yellow transit clip holding the pin and the rings fitted on the piston. When combining aftermarket pistons, use four pistons from the same batch so that their weights match.

The piston passes combustion pressure through the rod to the crankshaft; the rings seal the combustion chamber and control the oil film on the bore. In a turbocharged engine the crown works at high pressure and temperature, so ring wear shows as blue smoke, oil consumption, low compression and more blow-by from the breather. The gudgeon pin is fully floating and held by two circlips. The Dieselmax is a direct-injection engine: fuel is injected into the bowl in the piston crown and combustion starts there. Pistons in one engine should be close in weight, so when a single piston is replaced the weight difference is checked too.

Specifications

Compatibility

The part is listed for JCB 3CX and 4CX backhoe loaders. The SD code marks the Tier 3 turbo version of the Dieselmax 444; check the serial number on the engine plate. The catalogue also has the genuine version, OEM version and aftermarket version of this part. For standard bores there is the piston ring set 320/09299. Other parts are in JCB Dieselmax engine.

Fitting

When fitting the gudgeon pin the piston can be warmed slightly in warm oil; the pin must go in without force. Seat the circlips fully in their grooves. During the first hours after assembly, watch the oil level and exhaust smoke. After assembly, compression can be measured to compare the cylinders.