Camshaft drive
| Camshaft drive |
| Camshaft and tappets |
The engine has twin overhead camshafts with large diameter base circle, which allows a greater lift with small surface tension. The camshafts are driven by a timing chain equipped with a self-adjusting chain tensioner and act directly on the valves via hydraulic tappets.
The hydraulic tappets are automatically adjusted to changes in the length of the valves at different temperatures. They operate in an oil bath, with oil supplied via an oilway in the cylinder head. The main advantages are extremely quiet operation and high reliability.
The valves are manufactured in steel with chrome-plated stems. The heads of the exhaust valves are faced with stellite.
| Chain tensioner |
The chain tensioner is mounted in the cylinder head and is easily accessible for service. Tension is applied by a spring-loaded plunger, which keeps the slack side of the chain correctly tensioned via a pivoted guide rail. A ratchet with closely spaced teeth prevents the plunger and guide rail from returning.
The chain tensioner tensions the chain at short intervals, which gives good compensation for chain wear and consequently quieter operation.
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