Ktm Duke 640
The KTM Duke 640 was introduced in 1999 as an evolution of the Duke 620, featuring a refined single-cylinder 625cc LC4 engine and aggressive supermoto styling that helped define KTM's street naked identity. It was produced through 2006 and became iconic for its lightweight chassis, thumper character, and serious performance from a single-cylinder engine. The 640 Duke is widely regarded as one of the most characterful and capable single-cylinder street bikes of its era, influencing KTM's Duke lineup for decades to come.
55 hp
Power
60 Nm
Torque
148 kg
Weight
170 km/h
Top Speed
5.5–7.0 L/100km (typical real-world average)
Fuel
Naked
Body
What Buyers Should Know
LC4 Engine Quirks
The single-cylinder LC4 engine is known for vibration and can be temperamental when cold — always check for a smooth idle and listen for top-end ticking, which may indicate worn cam followers.
High Maintenance Costs
The Duke 640 requires frequent valve checks every 6,000 miles and has relatively expensive KTM-specific parts, so always ask for a full service history before buying.
Strong Cult Resale
Well-maintained examples hold value surprisingly well due to a loyal enthusiast community, but neglected bikes drop sharply — a full service record can significantly increase asking price.
Full Specifications
Rivals & Alternatives
Bikes that buyers cross-shop with the Ktm Duke 640
