Honda - Genuine Honda K-Series Lost Motion Assembly Spring (LMA) | 14820-PNA-013

The Honda K-Series Lost Motion Assembly (LMA) is a small but important component located in the cylinder head as part of the VTEC rocker-arm system. Its job is to control and maintain tension on the center/VTEC rocker arm when VTEC is not engaged. During normal low-RPM operation, the center rocker follows the high-lift VTEC cam lobe without controlling the valves; the LMA keeps that rocker properly loaded against the cam so it can follow the lobe smoothly instead of bouncing or slapping around. 

When VTEC activates, oil pressure locks the rocker arms together, allowing the high-lift cam profile to control valve operation. Because of this design, keeping the center rocker properly controlled when VTEC is disengaged is important to the smooth and reliable operation of Honda’s VTEC valvetrain.

Why are good LMAs important? Over time and repeated heat cycles, a worn or weakened lost motion assembly can lose tension. This can allow excessive movement of the center rocker arm and contribute to the familiar ticking, tapping, or chattering noise from the cylinder head. Fresh LMAs restore the intended tension, helping keep the rocker assembly controlled and reducing unwanted valvetrain movement and noise.

They are especially worth considering during a K-series cylinder-head rebuild, valvetrain refresh, or camshaft upgrade, or when diagnosing unexplained upper-engine valvetrain noise. 

“Restore proper VTEC rocker-arm control and eliminate the unwanted movement associated with worn K-Series lost motion assemblies. Genuine Honda 14820-PNA-013 LMAs maintain proper tension on the VTEC rocker mechanism for smooth, quiet and reliable valvetrain operation.”

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Ref No. 15 in the diagram pictured

Vehicle Fitment

• 2008-2012 Honda Accord
• 2010-2014 Honda CR-V
• 2006-2015 Honda Civic
• 2012-2015 Honda Crosstour
• 2013-2015 Acura ILX
• 2002-2006 Acura RSX
• 2004-2014 Acura TSX

LOCATION: BIN A-73