Shown below is the arrangement of a chain drive, which is used to transmit power from the crankshaft to the camshaft.

• It consists of chain sprockets mounted on the crankshaft & camshaft. There can be two or more chains.
• A chain-tightening arrangement is provided, as shown in the fig.
• The chain is guided by the guide bars, which has rubber shock-absorbing pads
• Flyweights are provided as they are the moment compensators.
• Oil spray nozzles are used to lubricate the chain & the wheels.

In the event of a chain link failure during engine operation, the following steps should be carried out:

• Turn the chain until the damaged link is positioned on the longest free end side of the chain, where it is easily accessible.
• Release tension on the chain to facilitate repair.
• Wrap a thin wire around the chain, a short distance from the damaged link, and pull the wire taut using a chain block. This ensures that the chain remains stable during repair.

Remove the Faulty Link:

• Chisel or grind off the riveted metal on the pin ends of the damaged link.
• Use a chain bursting tool:
  • Place the tool over the smallest part of the chain link.
  • Align the dismantling screws precisely over the ground pin ends.
  • Tighten the dismantling screws alternately to push the pins out of the link.
• Remove the damaged link plate and pin.

Install the Replacement Link:

• Replace the damaged plate and pin with a new spare.
• Rivet the ends of the new pin securely.
• If a second chain is present, replace the corresponding link in the other chain to ensure uniform wear and performance.

After the repair, adjust the chain tension to the correct setting.

Reasons for failure:

• Cyclic stresses resulting in fatigue failure cracks.
• Excessive wear due to improper lubrication.
• Overheating due to improper lubrication.

Setting the chain to the correct degree of tension initially:

• Turn the engine to bring the slack part of the chain on the same side as the lighter wheel.
• Place the spring & spring carrier in place. Tighten Nut 'C' till the required compression of spring is achieved (softly touching).
• Tighten nut 'B' till it touches the shaft (softly touching).
• Tighten nut 'C' further again till the shaft carrying carrier is up against the star (further compression will not affect the chain tension).
• The lock nuts A & D are then tightened & locking washers are bent in place.

Chain tightening: