FAST FACTS

1One

significant difference between two and four-stroke pistons is the lack of a scraper ring on the former type. The reason being four-strokes have a lot more oil in the crankcase which sloshes around and coats the lower barrel. When the piston descends, it needs to scrape the majority of the oil clean of the bore so consequently needs a special oil control ring to do this.

2Some

two-stroke pistons have two rings, while others have just one. The challenge is maximising compression while achieving minimum friction. A race engine is more likely to have just a single ring, as this minimises friction and maximises engine performance, while a road-focused engine’s design caters more for reliability and endurance. 3In a four-stroke motor, the highest mechanical losses are a consequence of the pistons and rings contacting. It’s the same situation on both two and four-stroke engines. 4Piston rings act as a thermal conductor for pistons, as they transfer the heat generated by combustion and dissipate it via rings to the barrel before eventually reaching the cooling system.