Mechanical tensioner pulley 320/08729, aftermarket, option 1

Mechanical tensioner pulley 320/08729 is an aftermarket part for the JCB Dieselmax 444 engine.

The mechanical tensioner pulley holds the belt tight through an adjustable arm; tension is set during fitting and then locked. A worn pulley bearing causes a hum and uneven belt wear; if the arm mounting loosens, the belt goes slack, squeals and slips. The photos show the arm and pulley assembly. The belt from the crank pulley drives the alternator, water pump and other ancillaries; a slack belt reduces their output and an overtight one loads the bearings. Correct tension matters for belt life and proper charging. If the arm pivot or adjusting slot is worn, the tension will not hold and the arm is replaced. The pulley face suits the back or the ribs of the belt. The arm has an oval slot for adjustment.

Specifications

Compatibility

The part is listed for JCB 3CX and 4CX backhoe loaders. The catalogue also has the aftermarket version of this part. Other parts are in JCB Dieselmax engine.

Fitting

Recheck the tension after a few hours of running; a new belt stretches a little at first. Fit the belt according to its direction arrow.