PRODUCT DETAILS
Honda Crank Pulley (13810-RRB-A01) - 06-11 Civic Si & RSX Type S (K20Z3/K20Z1/K20A2)
The crank pulley on your K20 does more than spin the belts, it's a harmonic damper, absorbing the torsional vibration the crankshaft produces on every combustion event. When the rubber bonding inside it degrades, it stops damping, and those vibrations go somewhere less forgiving. This is the genuine Honda replacement for the 2006-2011 Civic Si, the 2002-2006 RSX Type S, and the K20Z3, K20Z1, and K20A2 engines.
What A Failing Crank Pulley Looks Like
These fail in a specific, recognizable way, so it's worth knowing the signs.
The pulley is built in two pieces, an inner hub and an outer ring, bonded with rubber between them. That rubber absorbs vibration, and over years and heat cycles it degrades.
What you'll see is the outer ring separating or walking relative to the inner hub. Sometimes there's visible cracking or missing chunks of rubber. Sometimes the ring has shifted enough that your belt no longer tracks straight, which shows up as belt wear, squeal, or a wandering serpentine belt you can't explain.
The serious version is the outer ring letting go entirely at high RPM, which takes your accessory belt with it and can do real damage on the way out. On a K20 that spends time near redline, catching this before it fails is worth doing.
Why The Damping Matters
Worth understanding, because it explains why you can't just run any pulley.
A crankshaft doesn't rotate perfectly smoothly. Every combustion event twists it and it springs back, setting up torsional vibration along its length. Left unchecked, that vibration is genuinely destructive to the crank, the bearings, and everything driven off the front of the engine.
The damper absorbs it, and its damping characteristics are tuned to the frequencies a K-series specifically produces. A degraded pulley isn't just a belt problem, it's a component that's no longer protecting the bottom end of your engine from the vibration it was designed to control.
Grab A New Crank Pulley Bolt And Key
Worth adding to the order, since these are the small parts that make the job go right.
The crank pulley key (90704-PNA-000) indexes the pulley to the crankshaft. It's inexpensive, easy to nick or bend on removal, and a damaged key means a pulley that doesn't seat exactly right, which allows movement and eventually wallows out the keyway in the crank itself. Given you're already in there, there's no reason to reuse a marginal one.
The crank pulley bolt (90017-PCX-013) is torque-to-yield and takes a serious torque spec, so if yours has been off before, a fresh bolt is cheap insurance on a fastener you really don't want backing out.
Use The Genuine Part
The damping characteristics are the specification here, and they're tuned to the K-series.
Underdrive and lightweight pulleys exist and have their place on a dedicated track car, but they're a different product with real tradeoffs, including reduced damping. A cheap pulley that bolts on and spins isn't necessarily absorbing the frequencies your engine produces. If you want a factory-behaving K20 with proper vibration control, this genuine Honda pulley is the part.
Common In K-Swaps Too
Beyond stock replacement, this is a regular part in swap and build work.
The K20A2, K20Z1, and K20Z3 all use it, which covers a lot of what goes into K-swapped chassis. If you're assembling an engine from parts of unknown history, a fresh pulley is cheap insurance on a component that's easy to overlook and expensive to ignore, since a swapped engine's original damper could be any age.
Fitment
2006-2011 Honda Civic Si
2002-2006 Acura RSX Type-S
Covers K20A2, K20Z1, and K20Z3. Part number 13810-RRB-A01. Genuine Honda.
Who Should Grab One
This is for the Civic Si or RSX Type S owner who's found a separating pulley, a belt that won't track straight, or vibration that wasn't there before, and for anyone going through a high-mileage K20 who wants the damper fresh. The rubber degrades on a calendar as much as on an odometer, so on an engine this age it's worth doing. Add the key and bolt, torque it properly, and get the front of the engine back to doing its job.
Fits: 2006-2011 Honda Civic Si and 2002-2006 Acura RSX Type-S. Part number: 13810-RRB-A01. Engines: K20A2, K20Z1, K20Z3. Type: genuine Honda crank pulley and harmonic damper. Also common in: K-swap builds. Recommended: fresh crank pulley key (90704-PNA-000) and bolt (90017-PCX-013) when installing.