Crankshaft

Due to the arrangement of the spaces, the combustion chamber accommodates the four mushrooms of the valves and the centre hole of the spark plug without weakening the structure of the head. The solution with the spark plug in the centre of the four valves (two inlet valves and two smaller exhaust valves) enables even distribution of the mixture and optimum development of combustion with improved thermal yield of the engine and lower harmful emissions at the exhaust.

The camshafts turn on three supports and they are driven through toothed belts. The valve seats are fitted on the cylinder heads after heating them to a temperature of 100° + 120°C. The valve guides are force-fitted in their housings on the cylinder heads with interference and the inside diameter is perfected after assembly using a specific reamer and checked using a pair of go-no go gauges. The seals between the cylinder heads and crankcase are of the ASTADUR type. Due to the special material with which they are made, these seals are polymerized when the engine is running and harden considerably during use, therefore it is no longer necessary to tighten the cylinder heads at the first service coupon.

CRANKSHAFT

This is forged in high-strength, hardened and tempered steel. It rests on three main bearings and its end float is adjusted by two half rings housed in the rear main bearing. Six counterweights accurately balance the rotating masses. A set of grooves run inside the shaft to lubricate the main and connecting rod journals.

MAIN AND CONNECTING ROD HALF BEARINGS

These are of the three-metal, thin shell type subdivided into two dimensional classes. The main half bearings have a hole and groove for lubricating the rod journals.

FLYWHEEL

This is in cast iron, with two ring gears in hardened and tempered steel: one for connection with the starter motor and one for the rpm sensor facing it. The "T" notch for checking engine timing is stamped on the flywheel.

PISTONS AND CONNECTING RODS

The pistons in aluminium silicon alloy are subdivided into five dimensional classes and they are available as Spares in three other oversize classes.