🔍 Key Concepts

• Look closely at the cylinder heads and valve arrangement to decide if this is a two‑stroke or four‑stroke engine. • Check whether the crankcase is used for scavenging air or is simply an oil sump, which tells you if it is crankcase scavenged or not. • Look for any signs of blowers, turbochargers, or air pumps to decide if the engine is naturally aspirated.

💭 Think About

• In the illustration, do you see both intake and exhaust valves in the head, and do they suggest distinct intake and exhaust strokes, or does air enter through ports in the cylinder wall? • Does the underside of the piston appear to be used as a pumping chamber for scavenging air, or is it just in a lubricated crankcase? • Do you see any separate scavenge pump or blower connected to the intake, or does air seem to be drawn in only by the piston's movement?

✅ Before You Answer

• Verify whether the cylinders have valves in the head (typical of four‑stroke) versus ports in the cylinder wall (typical of crankcase‑scavenged two‑stroke). • Confirm if the crankcase space is clearly an oil-filled sump and not part of the air path for scavenging. • Check if there is no external blower or turbocharger shown, which would support the engine being naturally aspirated.