Heavy breathing, smoking, erratic idling and a thirst for oil are all signs that the smaller capacity OHV engines have advanced piston, piston ring and bore wear. An intermittent ‘clacking’ sound is a result of the camshaft followers having split and cracked. Oftenclosed points are a common cause of rough running.
A worn CVH will also emit blue smoke and breathe heavy, but an oily engine bay can also be down to the commonly-blown rocker cover gasket. A noisy top end can mean that the camshaft is damaged, due to the lifters being sludged up as a result of infrequently changed oil. Poor running is often caused by a worn distributor that’s advancing too early.