Repairing Stripped Primary Cover Drain Plug Threads on a 2006 Harley-Davidson FLHTC

One of the more common issues encountered during primary service on Harley Touring models like the 2006 FLHTC is a stripped drain plug thread in the primary cover. Over time, repeated removal and installation — especially if the plug was over-torqued or cross-threaded — can damage the soft aluminum threads.Most Common Repair: 1/2"-20 Thread InsertsFor the vast majority of Harley primary cover drain plug repairs (including most FLHTC, FLHR, FLHT, and similar models), the 1/2"-20 thread repair is the go-to solution. This size has been by far the most popular drain plug repair kit we’ve sold for Harley-Davidson primaries over the years. It restores the threads reliably and allows the use of a standard 1/2"-20 magnetic drain plug.Alternative Repair Option: 3/8"-24 Thread InsertsHowever, not every case fits the 1/2"-20 repair. We recently had a customer with a 2006 Harley FLHTC whose primary cover drain plug hole required a smaller repair. He successfully used a 3/8"-24 thread repair with .35" length inserts.

Insert Part Number: 03825 (.35" length 3/8"-24 inserts)
Kit Used: Time Sert 0382 (the full 3/8"-24 thread repair kit)

The customer reported that the repair went smoothly and has held up well since installation. He was kind enough to call back and share the outcome so we could pass the information along.If you’re working on a primary cover where the 1/2"-20 repair is too large or the threads are damaged in a way that requires a smaller oversize, the 3/8"-24 with .35" inserts is a proven alternative that works well on FLHTC and similar primary covers.Repair Tips for 2006 FLHTC Primary Drain Plug

Drain the primary oil completely and clean the area thoroughly.
Inspect the existing threads — determine whether 1/2"-20 or the smaller 3/8"-24 repair is appropriate.
Use the correct kit:
- Standard repair → 1/2"-20 kit (most common)
- Alternate repair → Kit 0382 with 03825 .35" inserts (3/8"-24)
Follow the kit instructions for drilling, tapping, and installing the inserts. Apply a light thread locker on the new drain plug during final assembly.
Torque to spec — typically 14–21 ft-lbs for primary drain plugs on these models (always check your service manual).

This repair allows you to reuse the original primary cover instead of replacing it, saving significant cost while restoring full functionality.If you have a stripped primary drain plug on your 2006 FLHTC (or any Harley), feel free to reach out — we can help you choose the right kit based on your specific situation. The 1/2"-20 is the most common, but as this customer proved, the 3/8"-24 with .35" inserts is a solid backup option when needed.

26th Jun 2026 DennisB