Chain drives are used by manufacturers, to give more flexibility in location of the camshaft, as well as ease of repair / replacement of parts at a lower cost; however this gives a more complex arrangement, with a large number of moving parts subject to wear and slackening, which can affect timing of fuel as well as other factors in engine operation.
the chain tension needs to be checked at intervals given in the maintenance schedule, or earlier if any doubt exists.
To carry out the checking, turn the engine to slacken the longest free length. At the middle of the longest free length, grasp the chain and try to pull it away from the guide bar, by a distance of approximately half a chain link. if it is possible to pull more, the chain is slack and needs to be re-tensioned.
Loosen the screw of chain tightener, and by turning the ‘loose’ plate of the chain tightener, adjust the tension of the chain as shown below.
Excessive chain tension overloads the chain and the bearings will wear unnecessarily. Insufficient chain tension may give rise to vibration, in the case of resonance, which, in the long run, may damage the chain.
Reference and Images
“Marine Engineering Practice” by Vikram Gokhale and N. Nanda