What is a Honda Lost Motion Assembly?

What is a Honda Lost Motion Assembly?

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So you’ve adjusted your valves in your Honda but the tapping noise just won’t go away. You’ve double checked your valve clearances and redone your work but the ticking sound is still there at idle and it’s driving you nuts. If you can’t figure out where the tapping under your DOHC VTEC valve cover is coming from, it could be that your Lost Motion Assembly has worn out.

The lost motion assembly in your DOHC Honda engine is a preloaded spring device that keeps your VTEC lobe from rattling when unlocked. Older Hondas use a fluid based lost motion assembly that hydraulically keeps your VTEC valvetrain in place. Later B series VTEC engines made the jump to a spring type spring system, that was far more reliable and durable than the older hydraulic units.

When your lost motion assembly has worn down, or the pad to your LMA has gone out it’s going to cause valvetrain noise in your VTEC engine. Over time your Honda VTEC LMA can lose the preloaded tension and sag, which can cause your center VTEC lobe to chatter when it’s not engaged.

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Because most of these scenarios are at idle, most people mistake their lost motion assembly failure to valves needed adjustment. If you are planning a LS VTEC build and want to know how to build a reliable LS VTEC, looking at upgrading your LMA is definitely a good decision.

If you’ve already got a motor swap in your Honda, there’s a few choices when it comes to upgrading your valvetrain. If you’ve got a DOHC B series VTEC engine swap in your car and want to step up to high lift cams, upgraded LMA’s are the only way to go.

How do I know I have a bad Lost Motion Assembly?

If you’ve adjusted your valves but that persistent ticking noise or tapping sound under your valve cover just won’t go away, chances are it’s your lost motion assembly. Because this preloaded spring device is meant to put designed load on your center lobe or the VTEC lobe, when it starts to sag your valvetrain chatter will increase.

Because your¬†DOHC VTEC engine in your Type-R, GSR, Civic or Integra with a B16A, B17A, B18C relies on this LMA it’s a good idea to check them when your engine starts making a lot of noise at idle. The Honda part numbers for these LMA units are 14820-PCB-003 and 14820-PCB-305 if you want to stick to the factory goods.

Do I need to replace my Lost Motion Assembly?

It’s a common question and a fair one to be honest. I mean who really wants to tear apart their B series cylinder head to get to the LMAs? However if you want to prevent long time or premature failure in your DOHC VTEC cylinder head proper maintenance is extremely important.

When your VTEC is not engaged your center lobe will flop around and has the chance to become damaged due to the vibration and movement. Your lost motion assembly is responsible for keeping tension on this lobe so that this does not happen.

Need an upgraded LMA but not sure where to turn? Check out our online store with the latest in Skunk2 and upgraded LMA kits that help you get your DOHC VTEC back on the road right away.

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