Valve Clearance

Valve clearance (also called valve lash or valve adjustment) refers to the small gap between the camshaft lobes and the valve train components (either rocker arms or tappets/shim-over-bucket systems). This gap is necessary to allow for thermal expansion when the engine heats up. If the clearance is too tight, valves may not fully close, leading to burned valves and power loss. If too loose, the engine becomes noisy and valve timing is affected.

Valve clearance checks are one of the more involved maintenance tasks on a motorcycle and are typically specified at intervals of 10,000-26,000 miles depending on the manufacturer. Some engines use screw-and-locknut adjusters (common on twins and singles) that are relatively easy to adjust. Others use shim-under-bucket or shim-over-bucket systems (common on inline-fours) that require removing the camshafts to change shim sizes — a more complex procedure.

For many riders, valve clearance checks are the maintenance item they're most likely to outsource to a mechanic, as it requires specific tools, precise measurements with feeler gauges, and mechanical confidence. However, if you're handy, it's a learnable DIY task that can save $200-500 per service. Always consult your motorcycle's service manual for the correct clearance specifications.

One detail that surprises many new riders is how rarely modern engines need valve adjustments compared to older motorcycles. Bikes from the 1970s-1980s required checks every 3,000-4,000 miles, while many current models go 26,000+ miles between checks — and some Honda and Yamaha models frequently show in-spec clearances even at 50,000+ miles. The other surprise: valve checks sometimes don't require adjustment at all. If you're buying a used bike, check service records for valve check history — a bike significantly overdue should raise concern about overall maintenance diligence.