The Con Rod or Connecting Rod is a heavy shaft with a ‘big end’ and a ‘small end’.

 

Each cylinder of the engine has one Con rod. The big end has a circular end which connects to one part of the crankshaft and the small end has a small circular connection to a shaft on the inside of each piston. Both ends have bearings to allow rotation.

 

The Con rod is pushed down with the combustion in the cylinder head chamber which forces the piston down via the Con rod to the crankshaft causing it to rotate.

 

If the engine is allowed to run for some reason without lubrication it will cause overheating and destruction of the bearings on either end of the Con rod. The complete removal and opening of the engine will be required to replace these bearings and in some cases, the con rod bearing seatings may have been damaged and the Con rod will also have to be replaced.