2003 — 2006
654cc LC4 Single-cylinder - Competition focused
Petrol
When idling in neutral, observe the engine casing for excessive 'LC4 tremor' or rattling, which can be an indicator that the main crankshaft bearings may benefit from an inspection in the future.
Shift through all gears under moderate load to check for any 'false neutrals' or gear jump, as these high-performance competition gearboxes can wear if the previous owner hasn't kept up with frequent oil changes.
While accelerating in a straight line, listen closely for any unusual top-end ticking; while the LC4 engine is naturally noisy, a metallic 'clatter' might suggest the cam follower bearings or rocker arms could require adjustment or replacement down the track.
Before your test ride, check the coolant reservoir and oil sight glass; look for any milky discoloration which can be a sign that the water pump seal is nearing the end of its service life.
Usually marks the point where valve clearances should be verified and the general chassis pivot points greased.
A common interval to evaluate the internal state of the piston rings and timing chain tensioner given the performance-oriented nature of the 660 SMC.
Generally seen as the period where comprehensive suspension service, including shock seals and fork oil, is recommended for optimal handling.
Check the engine oil levels religiously, as these high-compression singles can consume small amounts of oil during spirited riding.
Keep a close eye on your chain tension and sprocket wear, as the torque from the 660 LC4 can accelerate wear if not kept within spec.
Ensure the air filter is cleaned frequently; because this is a competition-derived engine, it thrives on clean airflow.
Monitor the electrical connectors for any signs of corrosion, which can sometimes occur on bikes of this age after exposure to the elements.
Maintain a strict regime for fluid changes, particularly the brake fluid, to ensure the powerful Brembo setup remains sharp.
Estimated repair costs if issues arise
If you notice coolant weeping from the weep hole, it is often a sign the seal is aging. It is a common maintenance item for the LC4 engine, and proactive replacement is a smart way to protect the engine internals.
To keep the top end running smoothly, many owners eventually look at replacing the rocker arm bearings as part of a long-term refresh to prevent premature wear on the camshaft.
Since this is a competition machine, the suspension works hard. Depending on how the bike has been ridden, you might eventually need to budget for a professional service to reset the damping and replace aging seals.
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Disclaimer: This report is generated with the assistance of AI analysis based on verified automotive data. While we strive for 100% accuracy, enthusiasts should always conduct physical inspections and consult service records. View Full Disclaimer