ACT 2002 Honda Civic XACT Flywheel Prolite

The ACT 600125 is an XACT Prolite flywheel for the K20-powered Honda Civic Si and Acura RSX, listed here for the 2002 Civic. At 7.8 lb it is the lightest flywheel ACT makes for this chassis. Buyers looking for it are usually building a track, autocross or rally EP3 Civic Si and want the K20 to rev as quickly as possible, or they are already replacing a clutch and want a forged flywheel that can be resurfaced instead of thrown away.

What the Prolite flywheel does in a K20 Civic Si

The flywheel bolts to the crankshaft, carries the starter ring gear and gives the clutch disc its rear friction surface. Every pound it carries has to be spun up and slowed down with each shift. ACT machines the 600125 from a heat-treated chromoly steel forging in one piece, with an induction-hardened ring gear of 119 teeth and an 8.5 inch (215 mm) friction surface, and computer balances it for high-rpm use. ACT lists it as SFI 1.1 certified.

ACT is clear about the trade-off. Its Prolite line is the lowest-inertia option, aimed at road racing and rally, and ACT describes drivability as reduced, with mild to moderate gear rattle. For a car that sees mostly street miles, ACT's 600295 Streetlite flywheel for the same cars weighs 11.4 lb and is easier to live with in traffic.

Symptoms that point to a flywheel replacement

• Clutch chatter or judder on takeoff that a new disc did not cure
• Hot spots, cracks or a dished friction face on the old flywheel
• Grinding or skipping when the starter engages, from damaged ring gear teeth
• Slip that began after the old flywheel was machined too thin
• Vibration that rises with rpm after a clutch job, pointing to an out-of-balance part

None of these sets a trouble code by itself. A slow-revving or flat-feeling engine with a check engine light is an engine fault to diagnose first.

How to confirm before you buy

Most flywheel faults are confirmed with the transaxle out: check the face for heat cracks and blue spots, measure runout with a dial indicator and inspect the ring gear. On the car, a pull in fourth from low rpm tells you whether the clutch is slipping; our slipping diagnosis guide covers the test and shift flare vs. slip helps read the tach. If you are weighing machining the factory part against replacing it, see flywheel resurface vs. replace.

Fitment

Our listing is titled for the 2002 Honda Civic. That means the 2.0L K20 Civic Si hatchback, not the 1.7L D17 Civic DX, LX or EX, which uses a different flywheel. ACT's own fitment table lists the 600125 for the 2002-2006 Acura RSX base and Type-S and the Honda Civic Si from 2002 through 2011, including the 2002-2004 Civic SiR and the 2008 Civic Mugen Si. Because K-series swaps are common in older Civics, check the engine code, match your clutch disc diameter and flywheel bolt pattern, or send us the year and VIN before ordering. More performance flywheels and clutch parts are in our hard parts category.

Install notes

• Pair it with a clutch rated for your power. ACT's H024X Xtreme pressure plate is one option for these cars.
• Inspect the rear main seal and the crank pilot area while the flywheel is off; oil contamination ruins a new disc.
• Use new flywheel bolts, torque them in a cross pattern to the factory spec and verify runout before the clutch goes on.
• Clean the friction surface with brake cleaner, then center the disc with an alignment tool.
• Refill the transaxle with Honda manual transmission fluid and bleed the clutch hydraulics with the fluid shown on the reservoir cap.
• Expect more gear rattle at idle and less forgiving launches than stock. ACT notes the flywheel can be resurfaced later with no extra parts needed.

Does the ACT 600125 fit a 2002 Civic LX or EX?

No. Those cars use the 1.7L D17 engine. ACT lists the 600125 for the K20-powered Civic Si and Acura RSX only.

How much does the 600125 weigh?

ACT lists it at 7.8 lb. The ACT 600295 Streetlite for the same cars is 11.4 lb.

Which years and models does ACT list for this flywheel?

The 2002-2006 Acura RSX base and Type-S, and the Honda Civic Si from 2002 through 2011, including the 2002-2004 SiR and the 2008 Mugen Si. Send us your VIN if your car has had an engine swap.

Is the Prolite good for a daily driver?

ACT recommends the Prolite for race use and says drivability is reduced, with mild to moderate gear rattle. Street-driven cars are usually better served by the Streetlite version.

Can it be resurfaced?

Yes. ACT says its flywheels are serviceable and can be resurfaced without buying additional parts.

Does it come with a warranty?

Yes, a 1-year warranty, which matches the 12 months ACT lists for this part.

• How to Diagnose Transmission Slipping
• Shift Flare vs. Slip: How to Tell Them Apart
• Automatic vs. Manual Transmission Repair Cost